Electrode for a contact start plasma arc torch and contact start plasma arc torch employing such electrodes

ABSTRACT

An electrode for a contact start plasma arc torch includes an elongated electrode body formed of an electrically conductive material. The electrode body is movable relative to the torch. A resilient element, contacting a proximal end of the electrode body, is used for imparting a separation force to the electrode body. The electrode body is adapted to overcome the separation force and engage a contact element of the torch when the torch is operated in a transferred arc mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 60/774,451, filed Feb. 17, 2006 and titled “Electrodefor a Contact Start Plasma Arc Torch and Contact Start Plasma Arc TorchEmploying Such Electrodes,” the entirety of which is hereby incorporatedby reference. This application is a continuation of U.S. Ser. No.11/709,315, filed on Feb. 20, 2007 now U.S. Pat. No. 8,115,136, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates generally to plasma arc torches and moreparticularly to electrodes and torches for contact start plasma arctorch applications.

BACKGROUND

Material processing apparatus, such as plasma arc torches and lasers arewidely used in the cutting and marking of metallic materials known asworkpieces. A plasma arc torch generally includes a torch body, anelectrode mounted within the body, a nozzle with a central exit orifice,electrical connections, passages for cooling and arc control fluids, aswirl ring to control the fluid flow patterns, and a power supply. Gasesused in the torch can be non-reactive (e.g., argon or nitrogen), orreactive (e.g., oxygen or air). The torch produces a plasma arc, whichis a constricted ionized jet of a plasma gas with high temperature andhigh momentum.

One method for producing a plasma arc in a plasma arc torch is thecontact start method. The contact start method involves establishingphysical contact and electrical communication between the electrode andthe nozzle to create a current path between them. The electrode and thenozzle can cooperate to create a plasma chamber within the torch body.An electrical current is provided to the electrode and the nozzle, and agas is introduced to the plasma chamber. Gas pressure builds up untilthe pressure is sufficient to separate the electrode and the nozzle. Theseparation causes an arc to be formed between the electrode and thenozzle in the plasma chamber. The arc ionizes the introduced gas toproduce a plasma jet that can be transferred to the workpiece formaterial processing. In some applications, the power supply is adaptedto provide a first electrical current known as a pilot current duringgeneration of the arc and a second current known as a transferred arccurrent when the plasma jet has been transferred to the workpiece.

Various configurations are possible for generating the arc. For example,the electrode can move within the torch body away from the stationarynozzle. Such a configuration is referred to as the “blow-back” contactstart method because the gas pressure causes the electrode to move awayfrom the workpiece. In another configuration, the nozzle can move awayfrom the relatively stationary electrode. Such a configuration isreferred to as the “blow-forward” contact start method because the gaspressure causes the nozzle to move toward the workpiece. In stillanother configuration, other torch components (e.g., the swirl ring) canbe moved between the stationary electrode and nozzle.

Certain components of the material processing apparatus deteriorate overtime from use. These “consumable” components include, in the case of aplasma arc torch, the electrode, swirl ring, nozzle, and shield.Furthermore, in the process of starting the torch using the contactstart method, various consumable components can become misaligned, whichreduces the useful life of the components as well as the accuracy andrepeatability of plasma jet location. Ideally, these components areeasily replaceable in the field. Nevertheless, replacing consumablecomponents can result in down time and reduced productivity.

In the blow-back method of contact starting a plasma arc torch, theelectrode is moved away from the nozzle to initiate a pilot arc betweenthe electrode and the nozzle. A proximal end of the electrode (e.g.,remote from the workpiece) engages a power contact that forms a part ofthe torch body. Movement of the electrode away from the nozzle alsomoves the power contact. Repeated use of the torch results in wear onboth the power contact and on the electrode. Replacing the electrode isroutine in plasma arc torch operation and the process is routinelyperformed. However, replacing the power contact involves disassemblingthe torch body and can be time-consuming and expensive because the powercontact is not designed to be a consumable component. Some blow-backtorches involve moving the power contact with respect to the relativelystationary torch body. Movement of such a power contact and theeffectiveness of the torch can be affected by the stiffness or rigidityof the power cable that connects the power contact to the power supply.

For example, FIG. 1 is a cross section of a known contact start plasmaarc torch. The system 100 includes a power supply (not shown) inelectrical communication over a current-carrying cable 104 with a powercontact 108 that provides current to the torch 112. The torch 112includes a cathode block 116 electrically insulated from and surroundingthe power contact 108. The power contact 108 abuts a proximal end 120 ofan electrically conductive electrode 124. A spring 128 disposed withinthe cathode block 116 reacts against a surface 132 of the cathode block116 to urge the power contact 108 and electrode 124 toward anelectrically conductive nozzle 136. The electrode 124 is urged intocontact with the nozzle 136 by the spring prior to initiation of an arcfor processing a workpiece (not shown).

A current path is established from the cable 104 to the power contact108, the electrode 124, and the nozzle 136. Electrical current can bepassed along the current path. The electrode 124 cooperates with thenozzle 136 to form a portion of a plasma chamber 140. A plasma gas canbe supplied to the plasma chamber 140 to increase pressure within theplasma chamber 140 and overcome the force provided by the spring 128.The pressure forces the electrode 124 and the power contact 108 awayfrom the nozzle 136. A potential difference develops between theelectrode 124 (e.g., the cathode) and the nozzle 136 (e.g., the anode)as the gap 144 between the electrode 124 and the nozzle 136 increases.An arc (not shown) ionizes gas particles and is initiated across the gap144 for workpiece processing.

One drawback of the system 100 is that the power contact 108 is requiredto move as the electrode 124 moves to initiate an arc. As the currentcarrying capacity of the cable 104 increases, the size of the cable 104increases, but the flexibility of the cable 104 decreases. The decreasedflexibility of the cable 104 reduces the versatility and maneuverabilityof the torch 112. Additionally, the power contact 108 and the cathodeblock 116 require relatively tight tolerances (e.g., with relativelysmall clearance between the power contact 108 and the cathode block116). The relatively tight tolerances position and guide the powercontact 108 during motion of the power contact 108, for example, duringinitiation of a pilot arc.

SUMMARY

There is a need for an electrode for use in a contact start plasma arctorch that optimizes operation of the torch without prematurely failing.Further, there is a need for a contact start torch that employs theconcepts herein to maximize component lifetime within existing torchdesigns. It is therefore an object of the invention to provide alonger-lasting electrode and components for use with an electrode in aplasma arc torch. Another object is to provide a configuration thatreduces wear on components of the torch that are not designed asconsumables. Yet another object is to provide aligning features withrespect to torch components during torch operation (e.g., pilot arc andtransferred arc mode).

In one aspect, an electrode for a plasma arc torch has a powerconnection in electrical communication with a power supply. Theelectrode includes an elongated electrode body formed of an electricallyconductive material and defining a longitudinal axis. The electrodeincludes a resilient element for passing substantially all of a pilotarc current between the power supply and the electrode body during pilotarc operation of the plasma arc torch. The resilient element performsboth electrical and mechanical functions and can be referred to as adual-function element of the torch. The resilient element comprises anelectrically conductive material to facilitate both carrying a pilot arccurrent and dissipating thermal heating associated with the pilot arccurrent to prevent the resilient element from melting during initiationof the pilot arc. The conductive material can be selected, for example,based on the current rating of the conductive material. The resilientelement comprises the path of least resistance and/or highestconductance for carrying the pilot current between the power connectionand the electrode body. Additionally, the mechanical properties of theresilient element facilitate movement of the electrode body for contactstarting the plasma arc torch. In some embodiments, the resilientelement aids in aligning the electrode body relative to the torch.

In some embodiments, the electrode body is longitudinally movablerelative to the torch. In some embodiments, the electrode body includesa reaction surface disposed in a spaced relationship relative to aproximal end of the electrode body that is positioned remotely from aworkpiece. The reaction surface is configured for electricalcommunication with the electrically conductive resilient element. Insome embodiments, the reaction surface includes a radially extendingflange formed integrally with the electrode body.

In some embodiments, the resilient element is secured relative to theelectrode body. For example, the resilient element can be secured by adiametral interference fit or a friction fit. In some embodiments, theresilient element is disposed adjacent a distal end of the electrodebody, and the distal end includes an emissive element. In someembodiments, the resilient element is formed integrally with theelectrode body. In some embodiments, the pilot arc operation includesinitiation of a pilot arc. In some embodiments, pilot arc operationincludes initiation of a pilot arc and a duration of time afterinitiation of the pilot arc before the arc is transferred to theworkpiece or before the torch is operated in transferred arc mode.

In some embodiments, the electrode further includes a hollow body formaintaining the resilient element and for slideably receiving theelectrode body.

In another aspect, there is an electrode for a plasma arc torch. Theelectrode includes an elongated electrode body formed of an electricallyconductive material defining a longitudinal axis and a distal end thatincludes an emissive element. The electrode body is movable relative tothe torch. The electrode includes a contact element. The contact elementincludes a first surface for facilitating electrical communication witha power supply and a second surface for facilitating electricalcommunication with a corresponding contact surface of the electrode bodywhen the torch is operated in a transferred arc mode. The second surfaceof the contact element is characterized by the absence of contact withthe contact surface of the electrode body during initiation of a pilotarc.

The electrode body can be axially movable relative to the torch. In someembodiments, the second surface is configured for physical contact withthe contact surface of the electrode body when the torch is operated intransferred arc mode. In some embodiments, the electrode body includes areaction surface for contact with a conductive resilient element anddisposed in a spaced relationship relative to a proximal end of theelectrode body. The proximal end is disposed remotely from the distalend that includes the emissive element. The reaction surface can bedefined by a radially extending flange formed integrally with theelectrode body.

In some embodiments, the electrode includes an electrically conductiveresilient element in electrical communication with at least one of thecontact element or the electrode body. The resilient element can beformed integrally with at least one of the electrode body or the contactelement. In some embodiments, the resilient element is disposed adjacenta distal end of the electrode body. The resilient element can beretained by the electrode body. In some embodiments, the electrode bodyincludes a reaction surface formed integrally with the electrode body.The resilient element can be disposed between the reaction surface andthe second surface of the contact element.

In some embodiments, the resilient element is configured to passsubstantially all of a pilot arc current between the power supply andthe electrode body during pilot arc operation. The resilient element caninclude at least one of a spring or a wire. In some embodiments, atleast a portion of the contact element slideably engages the electrodebody. In some embodiments, a portion of the contact element canfacilitate passage of a pilot arc current between the contact elementand the electrode body when the contact element slideably engages theelectrode body. The contact element can be retained by the electrodebody. In some embodiments, the contact element includes a connectivemember that defines an aligning surface for restraining radial movementof the electrode body. The connective member can be formed integrallywith the contact element. In some embodiments, the electrode bodyincludes a receptacle disposed adjacent a proximal end of the electrodebody that is remote from a workpiece. The receptacle can be configuredto hinder disengagement of the contact element from the electrode body.

In another aspect, there is a contact element for conducting currentbetween a power supply and a torch electrode slideably mounted within atorch body of a contact start plasma arc torch. The contact elementincludes a first surface for facilitating electrical communication withthe power supply and a second surface for electrical communication witha contact surface defined by a proximal end of the torch electrode. Whenthe torch electrode is in physical contact with the second surface, atleast a portion of a transferred arc current passes through the contactelement and between the power supply and the torch electrode foroperating the torch in a transferred arc mode. The contact elementincludes an electrically conductive resilient element disposed adjacentthe electrode body for passing substantially all of a pilot arc currentfrom the power supply to the electrode body during a pilot arcoperation.

In some embodiments, a connective member extends from the second surfaceto slideably engage the electrode body. The connective member can beformed integrally with the second surface. In some embodiments, theconnective member includes a third surface configured to pass a portionof the transferred arc current between the power supply and theelectrode body when the torch is operated in transferred arc mode. Insome embodiments, the contact element includes a receptacle portion forsurrounding a portion of a proximal end of the electrode body. Theresilient element can be disposed within the receptacle portion of thecontact element. In some embodiments, at least one of the first surfaceor the second surface defines an annular surface.

In some embodiments, the contact element includes a third surface forelectrical communication with the power supply and for passing a portionof a transferred arc current between the power supply and the electrodebody when the torch is operated in a transferred arc mode. In someembodiments, the contact element includes an aligning portion definingan axis. The aligning portion is disposed in a spaced relationship witha proximal end of the electrode body and is configured to restrainradial movement of the electrode body.

In another aspect, an electrode for a plasma arc torch is featured. Theelectrode includes an elongated electrode body formed of an electricallyconductive material and defining a longitudinal axis. The electrode bodyincludes a distal end defining a bore for receiving an emissive elementand a proximal end defining a contact surface for electricalcommunication with a power supply. The electrode body includes areceptacle disposed within the proximal end of the electrode bodyconfigured to receive at least a portion of a contact element. A firstportion of the contact element is physically remote from the electrodebody during initiation of a pilot arc, and the first portion of thecontact element is for passing substantially all of a transferred arccurrent between a power supply and the electrode body when the torch isoperated in transferred arc mode. The bore and the receptacle areseparated by the electrode body.

In some embodiments, at least a portion of the contact surface isdisposed within the receptacle. The contact element can include anannular configuration. In some embodiments, the receptacle includes acylindrical portion and a restraint surface disposed at a proximal endof the receptacle for reacting against a portion of the contact elementto hinder disengagement of the contact element from the receptacle. Therestraint surface can be an annular configuration.

In some embodiments, the cylindrical portion is defined by a firstdiameter, the restraint surface includes a second diameter, and a distalregion of a connective member of the contact element defines a thirddiameter such that the third diameter is greater than the seconddiameter and less than the first diameter. The distal region can be adistal end of the connective member. In some embodiments, the receptacleincludes a surface radially dimensioned along an axis of the receptaclefor restraining radial movement of the electrode body. Theradially-dimensioned surface is for physical contact with the portion ofthe contact element received by the receptacle.

In some embodiments, the electrode body includes a reaction surfacedisposed in a spaced relationship relative to the contact surface. Thereaction surface can be a radially extending flange formed integrallywith the electrode body. In some embodiments, the electrode includes anelectrically conductive resilient element that is retained by theelectrode body. The reaction surface can be for contact with theresilient conductive element. The resilient element can be retained by adiametral interference fit. The resilient element can be disposed withthe receptacle.

In another aspect, a contact element for conducting current between apower supply and an electrode body slideably mounted with a torch bodyof a contact start plasma arc torch is provided. The electrode bodyincludes a distal end that includes an emissive element. The contactelement includes a first surface for facilitating electricalcommunication with the power supply and a second surface forfacilitating electrical communication with the proximal end of theelectrode body. The second surface is not in contact with the proximalend during initiation of a pilot arc and is in contact with the proximalend during a transferred arc mode such that at least a portion of atransferred arc current from the power supply passes between the firstand second surfaces of the contact element to the electrode body whenthe torch is operated in the transferred arc mode.

In some embodiments, the contact element includes an electricallyconductive resilient element disposed adjacent the electrode body. Theresilient element is for passing substantially all of a pilot arccurrent between the power supply and the electrode body during pilot arcinitiation. The contact element can include a connective member disposedbetween the second surface and the electrode body. In some embodiments,the connective member is formed integrally with the second surface. Insome embodiments, the connective member defines an axis and an aligningsurface in a spaced relationship with the proximal end for restrainingradial movement of the electrode body. In some embodiments, the firstsurface, the second surface, or both define an annular surface.

The contact element can include a swirl ring portion. In someembodiments, the contact element is formed integrally with the swirlring portion. The swirl ring portion can impart radial motion to a gasflowing through the plasma arc torch. The swirl ring portion can alsoinsulate the electrode body from the nozzle and direct the gas towards aportion of the electrode body defining a plurality of fins. The swirlring portion can also restrain radial movement of the electrode body inthe torch. In some embodiments, the swirl ring portion can perform allof these functions. In some embodiments, the swirl ring portion performsone or more of these functions. The functions not performed by the swirlring portion can be performed by one or more discrete components.

In another aspect, a plasma arc torch is provided. The plasma arc torchincludes a power supply for providing current to the torch. The torchincludes a plasma chamber defined by a nozzle and an electricallyconductive electrode body slideably mounted within the torch along anaxis defined by a proximal end of the electrode body and a distal end ofthe electrode body. The proximal end defines a contact surface, and thedistal end is disposed adjacent an exit orifice of the nozzle. The torchincludes a power contact disposed in a stationary position relative tothe plasma chamber. The power contact is in electrical communicationwith the power supply. The torch includes a resilient conductive elementfor passing substantially all of a pilot arc current between the powercontact and the contact surface of the electrode body during pilot arcoperation. The torch includes a contact element. The contact elementincludes a first surface in electrical communication with the powercontact and a second surface for electrical communication with acorresponding contact surface of the electrode body. The contact elementis capable of passing a transferred arc current between the power supplyand the electrode body during transferred arc mode.

In some embodiments, the resilient conductive element biases theelectrode body toward the nozzle. In some embodiments, the contactelement is disposed in a stationary position relative to the electrodebody. The contact element can be formed integrally with the powercontact. In some embodiments, the torch includes a shield defining anexit port positioned adjacent an exit orifice of the nozzle. The shieldcan be mounted on a retaining cap that is supported on a torch body ofthe plasma arc torch. In some embodiments, the torch includes a swirlring that imparts radial motion to gas flowing through the torch.

In another aspect, a plasma arc torch is provided. The plasma arc torchincludes a power supply for providing current to the torch. The torchincludes a plasma chamber defined by a nozzle and an electricallyconductive electrode body slideably mounted within the torch along anaxis defined by a proximal end of the electrode body and a distal end ofthe electrode body. The electrode body defines a contact surface, andthe distal end is disposed adjacent an exit orifice of the nozzle. Thetorch includes a power contact disposed in a stationary positionrelative to a plasma chamber and is in electrical communication with thepower supply. The torch includes a resilient conductive element forpassing substantially all of a pilot arc current between the powercontact and the contact surface of the electrode body during pilot arcoperation of the plasma arc torch. The resilient conductive elementbiases the electrode body toward the nozzle.

In some embodiments, the power contact includes a first surface forfacilitating physical contact and electrical communication with acorresponding second contact surface of the electrode body when thetorch is operated in a transferred arc mode. The first surface of thepower contact is characterized by the absence of contact with thecorresponding second contact surface of the electrode body duringinitiation of a pilot arc.

In another aspect, there is an electrode for a plasma arc torch inelectrical communication with a power supply. The electrode includes anelongated electrode body formed of an electrically conductive materialand defining a longitudinal axis. The electrode body includes a firstsurface for electrical communication with a first conductive element forfacilitating passage of a pilot arc current between the power supply andthe electrode body during initiation of a pilot arc. The electrode bodyalso includes a second surface positioned remotely from the firstsurface. The second surface is capable of physical contact andelectrical communication with a corresponding surface of a power contactfor facilitating passage of substantially all of a transferred arccurrent between the power supply and the electrode body duringtransferred arc operation. The second surface of the electrode body ischaracterized by the absence of contact with the corresponding surfaceof the power contact during initiation of the pilot arc.

In some embodiments, the electrode body is longitudinally movablerelative to the torch. Although the embodiments described hereinprimarily relate to longitudinal movement of the electrode body withinthe torch, some embodiments feature an electrode body that is movable ina direction other than longitudinal along an axis. For example, theelectrode body can move in a direction transverse to a longitudinal axisduring initiation of a pilot arc or other torch operation. The electrodebody can also move rotationally about the axis. In some embodiments,other movement of the electrode body occurs that is a combination oflongitudinal, transverse, or rotational motion (e.g., a twisting orbending motion).

In another aspect, a plasma torch component for receiving an electrodeis provided. The component includes an elongated hollow body and anelectrically conductive resilient member for facilitating electricalcommunication of a pilot arc. The elongated hollow body has a first endand a second end. The elongated hollow body includes (a) an interiorsurface, (b) one or more of a contour, step, or flange located on theinterior surface and disposed between the first end and the second endof the hollow body, the one or more of the contour, step or flangedefining a shaped opening adapted for slideably receiving acomplementary-shaped portion of the electrode, (c) a first opening inthe first end of the hollow body sized to receive an electrical contactelement, and (d) a second opening in the second end of the hollow bodysized to slideably receive the electrode. The electrically conductiveresilient member is disposed within the hollow body, such that theresilient member is at least partially maintained within the hollow bodyby the one or more of the contour, step, or flange, and wherein theresilient member aligns with the first opening.

In some embodiments, the hollow body of the component further includes aplurality of holes adjacent to the second opening of the hollow body forimparting a swirling flow on a gas. An embodiment also includes acontact element disposed in the first end of the hollow body. In thisembodiment, the contact element maintains the resilient member withinthe hollow body and facilitates electrical coupling between theresilient member and a power supply.

In another aspect, an electrode for a contact start plasma arc torch isprovided. The electrode includes an elongated electrode body made of anelectrically conductive material and a second end positioned adjacent tothe electrode body. The electrode body defines a longitudinal axis and adistal end for housing an emissive element. The second end defines anaxially extensive portion having a first length along a first directionand a second length along a second direction. The second length of theaxially extensive portion being greater than the first length.

In some embodiments, the first direction and the second direction of theaxially extensive portion define a surface orthogonal to thelongitudinal axis. In certain embodiments, the first and seconddirections are perpendicular. The electrode can include two or moreaxially extensive portions, each respective axially extensive portionhaving a respective first length and a respective second length greaterthan the respective first length. In certain embodiments, the two ormore axially extensive portions are disposed in an equiangularconfiguration about the axis. A value for the operating current fortransferred arc operation of the plasma arc torch can be associated withthe number of the two or more axially extensive portions. That is, aspecific operating current can correspond to a specific number ofaxially extensive portions located on the electrode body.

In some embodiments, the first direction and the second direction of theaxially extensive portion extend radially away from the axis. In oneembodiment, the first and second directions define a surface thatincludes a first region and a second region. The first region is inelectrical communication with a resilient element for passingsubstantially all of a pilot arc current therebetween during pilot arcinitiation. The second region is moved into physical contact andelectrical communication with a power contact for transferred arcoperation. In certain embodiments, the power contact is in electricalcommunication with a power supply. The power contact includes a firstcontact surface for physical contact and electrical communication withthe second region and a second contact surface for electricalcommunication with the resilient member.

In some embodiments, the second end and the electrode body areintegrally formed. In certain embodiments, the electrode furtherincludes a swirl ring defining an interior surface disposed relative toa shoulder. The shoulder defines a complementary contoured perimeter tofacilitate passage of the second length therethrough when the secondlength and the complementary contoured perimeter are aligned. In certainembodiments, the shoulder resists passage of the axially extensiveportion therethrough when the second length and the complementarycontoured portion are not aligned. The complementary contoured perimetercan define a third length greater than the second length. In someembodiments, the second length of the axially extensive portion issubstantially equal to a width of the electrode body.

In another aspect, a swirl ring for a contact start plasma arc torch isprovided. The swirl ring includes (a) a hollow body formed of aninsulative material along a longitudinal axis and defining an exteriorsurface and an interior surface, (b) one or more gas passagewaysextending from the exterior surface to the interior surface, and (c) ashoulder portion disposed relative to the interior surface and defininga contoured opening capable of receiving a complementary-shaped portionof an electrode body.

In some embodiments of this aspect, the shoulder portion permits thecomplementary-shaped portion of the electrode body to pass therethroughwhen the contoured opening and the complementary-shaped portion arealigned. In certain embodiments, the shoulder portion resists passagetherethrough of the complementary-shaped portion of the electrode bodywhen the contoured opening and the complementary-shaped portion are notaligned. The shoulder portion can include a reaction portion to limit anangular displacement of the electrode body. In one embodiment, thecontoured opening defines an inner diameter and an outer diameter. Theswirl ring can also include two or more portions in thecontoured-opening disposed in an equiangular configuration about theaxis, the two or more portions defined by the outer diameter of thecontoured opening.

In another aspect, a component for a contact start plasma arc torch isprovided. The component includes a hollow body defining a longitudinalaxis and an interior surface of the body. The interior surface of bodyincludes one or more of a contour, step, or flange defining a shapedopening capable of slideably receiving along the axis acomplementary-shaped portion of an electrode body. The shaped openinghas a first length along a first direction and a second length along asecond direction. The second length is greater than the first length.

In some embodiments, the component further includes a swirl ring portiondefining an exterior portion, an interior portion and one or more holespassing from the exterior portion to the interior portion for impartinga swirling motion to a fluid. The swirl ring portion can be formedintegrally with the hollow body. In some embodiments, the contour, stepor flange contacts a corresponding surface of a resilient element tohinder removal of the resilient element from the torch.

In another aspect, an electrode for a contact start plasma torch isprovided. The electrode includes an elongated electrode body and asecond end positioned adjacent to the electrode body. The elongatedelectrode body is made of an electrically conductive material anddefines a longitudinal axis and a distal end for housing an emissiveelement. The second end defines a first surface having a first diametercentered about the longitudinal axis and one or more regions proximallyextending from the first surface. Each one of the one or more regionshas a portion shaped to provide physical contact and electricalcommunication with a resilient conductive element to facilitate flow ofa pilot current.

In some embodiments of this aspect, the first surface of the second endof the electrode is moved into physical contact and electricalcommunication with a corresponding surface of a power contact tofacilitate passage of a transferred arc current. In certain embodiments,the electrode further includes a second surface positioned relative tothe first surface. The second surface is moved into physical contact andelectrical communication with a corresponding surface of a power contactto facilitate passage of a transferred arc current. In some embodiments,the second surface is parallel to the first surface and positioneddistally relative to the first surface or positioned proximally relativeto the first surface.

In some embodiments, the one or more regions proximally extending fromthe first surface of the second end are substantially parallel to thelongitudinal axis. Each of the one or more regions can define a seconddiameter smaller than the first diameter. In some embodiments, each ofthe one or more regions are diametrally disposed equidistant from thelongitudinal axis.

In another aspect, an electrode for a contact start arc torch isprovided. The electrode includes an elongated body made of anelectrically conductive material and defining a longitudinal axis and adistal end for housing an emissive element and a second end positionedadjacent the electrode body. The second end includes a means forslideably engaging an interior surface of a component of the plasma arctorch along the axis, a means for electrical communication with aresilient element during pilot arc initiation to facilitate flow of apilot current therebetween, and a means for electrical communicationupon movement into physical contact with a power contact duringtransferred arc operation.

In another aspect, an electrode for a contact start plasma arc torch isprovided. The electrode includes (a) an elongated electrode body made ofan electrically conductive material and defining an electrode width, theelongated body is slidably attachable to an adjacent member, (b) adistal end of the electrode body, (c) an emissive element located at thedistal end of the electrode body, (d) a second end of the electrode bodyhaving a surface for receiving an operational current, and (e) a radialextensive portion located at a position between the distal end and thesecond end of the electrode body. The radial extensive portion has asurface for receiving a pilot arc current. The radial extensive portionhas a first portion with a first length and a second portion with asecond length. The second length is greater than the electrode width andthe first length.

In other embodiments of the invention, any of the aspects above caninclude one or more of the above features. One embodiment of theinvention can provide all of the above features and advantages. Theseand other features will be more fully understood by reference to thefollowing description and drawings, which are illustrative and notnecessarily to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a known contact start plasma arc torch.

FIG. 2A is an exploded view of an electrode body, a conductive resilientelement, and a power contact, featured in embodiments of the invention.

FIG. 2B illustrates a cross section of an exemplary contact start plasmaarc torch employing the components of FIG. 2A prior to pilot arcoperation.

FIG. 2C illustrates a cross section of the plasma arc torch of FIG. 2Bduring transferred arc mode.

FIG. 3A is a cross section of an exemplary embodiment of an electrodefor use in a contact start plasma arc torch.

FIG. 3B is a more detailed illustration of the components of theelectrode of FIG. 3A prior to assembly of an embodiment of theelectrode.

FIG. 4A depicts a cross section of an exemplary contact start plasma arctorch including illustrative components in a configuration prior topilot arc operation.

FIG. 4B illustrates a cross section the plasma arc torch of FIG. 4Aincluding illustrative components in a configuration during transferredarc mode.

FIG. 5A depicts a cross section of an exemplary electrode including acontact element and a resilient conducting element disposed within areceptacle of the electrode body.

FIG. 5B depicts the electrode of FIG. 5A disposed in a transferred arcmode.

FIG. 6A depicts a cross section of an exemplary electrode including acontact element and resilient conducting element disposed at a proximalend of the electrode body.

FIG. 6B depicts the electrode of FIG. 6A disposed in a transferred arcmode.

FIG. 7A depicts a partially exploded view of an exemplary contactelement, resilient element, and power contact that embody principles ofthe invention.

FIG. 7B depicts the components of FIG. 7A disposed in a plasma arc torchoperation.

FIG. 8A depicts a cross section of another embodiment of an electrodebody, resilient conductive element, and contact element prior toinstallation within a plasma arc torch.

FIG. 8B illustrates the configuration of the components of FIG. 8Aduring transferred arc mode.

FIG. 9 depicts a cross section of another embodiment of an electrodethat embodies the invention.

FIG. 10A is a perspective view of an exemplary contact element andresilient conductive element.

FIG. 10B is a cross-sectional view of a portion of a plasma arc torchemploying the components of FIG. 10A during pilot arc operation.

FIG. 11A depicts an exemplary contact element for use in a contact startplasma arc torch.

FIG. 11B depicts the contact element of FIG. 11A rotated 90° about avertical axis.

FIG. 12A is a cross-sectional partial perspective view of an assemblyfor a contact start plasma arc torch.

FIG. 12B is an exploded perspective view of the assembly of FIG. 12A.

FIG. 12C is an elevational view of a portion of the assembly of FIG.12A.

FIG. 13A is a perspective view of an electrode for a contact startplasma arc torch.

FIG. 13B is an elevational view of an assembly for use with theelectrode of FIG. 13A.

FIG. 14A is a perspective view of an electrode for a contact startplasma arc torch.

FIG. 14B is an elevational view of an assembly for use with theelectrode of FIG. 14A.

FIG. 15A is a perspective view of an electrode for a contact startplasma arc torch.

FIG. 15B is an elevational view of an assembly for use with theelectrode of FIG. 15A.

FIG. 16 is a perspective view of an electrode for a contact start plasmaarc torch.

DETAILED DESCRIPTION

FIG. 2A is an exploded view of an electrode body, a conductive resilientelement, and a power contact, featured in embodiments of the invention.The system 200 includes an electrode body 202, a resilient conductiveelement 204, and a power contact 206 (also referred to as a powerconnection). The power contact 206 is in electrical communication with apower supply (not shown), for example, by a power cable (e.g., the powercable 104 of FIG. 1). The power supply provides to the power contact 206the electrical current used to operate a plasma arc torch, similar tothe torch 112 of FIG. 1. The electrode body 202 includes a reactionsurface 208 that is configured for electrical communication with theresilient conductive element 204. The reaction surface 208 is disposedin a spaced relationship with a proximal end 210 of the electrode body202. In some embodiments, the reaction surface 208 defines a flangeextending radially from the longitudinal axis A. In some embodiments,the reaction surface 208 is formed integrally with the electrode body202. For example, the reaction surface 208 can be fabricated from thesame material as the electrode body 202 or fabricated from a differentmaterial but bonded or secured to the electrode body 202.

The proximal end 210 of the electrode body 202 is disposed oppositelyfrom the distal end 212. In the illustrated embodiment, the diameter ofthe distal end 212 is greater than the diameter of the proximal end 210to allow the resilient conductive element 204 to surround the proximalend 210 when installed in the torch. Stated differently, the diameter ofthe proximal end 210 is less than the inside diameter of the resilientconductive element 204. In other embodiments, the proximal end 210 has adiameter equal to or greater than that of the distal end 212.

The power contact 206 includes a surface 214 for reacting against theresilient conductive element 204. The resilient conductive element 204reacts against the relatively stationary surface 214 and against thereaction surface 208 of the relatively moveable electrode body 202 tobias the electrode body away from the power contact 206 during pilot arcoperation. The electrode body 202 defines a contact surface 216 that isconfigured for physical contact and electrical communication with acorresponding surface 218 of the power contact 206. During the latterportion of pilot arc operation and during transferred arc mode, thecontact surface 216 is in an abutting relationship with thecorresponding surface 218. The portion 220 of the power contact 206adjacent the surface 218 and extending to the surface 214 defines adiameter such that the resilient conductive element 204 surrounds theportion 220.

In some embodiments, the power contact 206 can be fabricated as a partof the power contact 108 of FIG. 1 (e.g., by machining the power contact108 to include the features of the power contact 206). Such embodimentsallow a user to employ the concepts described with respect to FIG. 2A inthe existing torch system 112 of FIG. 1. In some embodiments, the powercontact 108 can be positioned in the blown-back position of FIG. 1 bymachining a groove in the power contact 108 and securing the powercontact 108 with respect to the torch 112 with a clip or a retainingring (not shown). In this way, the power contact 108 remains stationaryrelative to the torch 112 during both pilot arc operation andtransferred arc operation. In general, any of the embodiments describedherein can be used with the torch system 112 of FIG. 1 by modifying thepower contact 108 in accord with the principles described herein.

The relatively stationary power contact 108 requires less flexibilityfrom the power cable. An exemplary current suitable for use as a pilotarc current is between about 10 and about 31 amps. The electricalcurrent during transferred arc operation can be up to about 200 amps.However, electrical currents greater than about 200 amps are within thescope of the invention, e.g., 400 amps. In some embodiments, the powercontact 108 is fabricated from tellurium copper, brass, copper, or othermaterials suitable for passing current both during pilot arc operationand transferred arc operation.

In general, pilot arc operation refers to a duration of time between theprovision of electric current to the electrode body 202 and the transferof the plasma arc to the workpiece. More specifically, pilot arcoperation can include initiation of the pilot arc and some duration oftime after initiation of the pilot arc but prior to the transfer of thearc to the workpiece. Some torch designs include a safety mechanism toterminate pilot arc operation after a predetermined amount of timeirrespective of whether the plasma arc has been transferred to theworkpiece. Such mechanisms are designed to prolong the operational lifeof torch components and promote safety by limiting the amount of timethe torch is operated without a specific application (e.g., processing aworkpiece).

In some embodiments, the resilient conductive element 204 is secured toeither the electrode body 202 or the power contact 206. In otherembodiments, the resilient conductive element 204 is secured to both theelectrode body 202 and the power contact 206. For example, the resilientconductive element 204 can be secured by welding, soldering, bonding, orotherwise fastening to the electrode body 202 or the power contact 206.In some embodiments, the resilient conductive element 204 is secured tothe proximal end 208 of the electrode body 202 by a diametralinterference fit or other type of friction fit. For example, an outerdiameter of the proximal end 208 of the electrode body may be slightlylarger than an inner diameter of the resilient conductive element 204.In some embodiments, the proximal end 208 of the electrode body 202features an extension portion (not shown) having an inner diameter thatis smaller than the inner diameter of the resilient conductive element204. The extension portion can be formed integrally with electrode body202 or otherwise secured to the electrode body 202. Such a configurationpermits the electrode body 124 of FIG. 1 to be used, for example, in thetorch 240 of FIG. 2B.

In some embodiments, the portion 220 of the power contact 206 is taperedor in a frustoconical shape along the longitudinal axis A. In someembodiments, the electrode body 202 can include a radially extensiveshoulder (not shown) having a diameter that is greater than the insidediameter of the resilient conductive element 204 such that advancing theresilient conductive element toward the distal end 212 of the electrodebody 202 past (e.g., over) the radially extensive shoulder hinders theresilient conductive element 204 from disengaging the electrode body 202axially towards the proximal end 210.

In some embodiments, a distal face (not shown) of the shoulder is thereaction surface of the electrode body 202. A similar diametralinterference fit can be used with respect to the power contact 206. Forexample, the resilient conductive element 204 can be advanced axiallyaway from the electrode body 202 past the surface 214 of the powercontact such that the face 222 of the surface 214 opposite the portion220 hinders disengagement of the resilient conductive element 204 fromthe power contact. In some embodiments, the interface between the face222 and the resilient conductive element 204 establishes a current pathfrom the power contact 206.

In some embodiments, the resilient conductive element 204 is disposed ina spaced relationship with the distal end 212 of the electrode body 202instead of the proximal end 210. The distal end 212 generally includesan emissive element (not shown) such as hafnium for more efficientplasma arc generation and workpiece processing. In some embodiments, theresilient conductive element 204 is formed integrally with the electrodebody 202 or the power contact 206. For example, the resilient conductiveelement 204 can be formed from the same material as the electrode body202. In other embodiments, the resilient conductive element 204 isbonded or secured to the electrode body 202 to hinder disengagement fromthe electrode body 202 under normal operational conditions (e.g., gaspressure and/or the influence of gravitational or other forces).

FIG. 2B illustrates a cross section of an exemplary contact start plasmaarc torch employing the components and concepts of FIG. 2A. Theconfiguration of FIG. 2B illustrates the torch 240 prior to pilot arcoperation. The torch 240 includes the electrode body 202, the resilientconductive element 204, and the power contact 206 of FIG. 2A, mountedwithin a torch body 242. A nozzle 244 and a swirl ring 246 are alsomounted to the torch body 242. The power contact 206 is positionedrelatively stationary with respect to the moveable electrode body 202.The power contact 206 is positioned oppositely from the distal end 212of the electrode body 202 (e.g., at the back end of the torch 240). Thedistal end 212 of the electrode body 202 includes an emissive element248 substantially aligned with an exit orifice 250 of the nozzle 244. Insome embodiments, the emissive element 248 and the exit orifice 250 aresubstantially centered about the longitudinal axis A. The swirl ring 246is positioned to in part restrain radial motion of the electrode body202 within the torch body 242. For example, the swirl ring 246 can bemanufactured to permit a relatively small gap between the swirl ring 246and one or more radial fins 252 of the electrode body 202.

The resilient conductive element 204 reacts against the reaction surface208 of the electrode body 202 and against the surface 214 of the powercontact 206 to urge the electrode body 202 into abutting relation withthe nozzle 244. Gas flows into a plasma chamber 254 formed between theelectrode body 202 and the nozzle 244, and a pilot current is passedfrom the power supply (not shown) to the power contact 206.

Gas pressure builds within the plasma chamber 254 until the pressure issufficient to overcome the force provided by the resilient conductiveelement 204. The gas pressure moves the electrode body 202 away from thenozzle 244 and into an abutting relationship with the power contact 206.The electrode body 202 moves substantially along the longitudinal axisA. As the electrode body 202 is moved away from the nozzle 244 by gaspressure, an arc is generated or initiated in the plasma chamber 254.The arc ionizes the gas within the plasma chamber 254 to form a plasmaarc or jet that exits the orifice 250 of the nozzle 244 and istransferred to the workpiece (not shown).

The resilient conductive element 204 is configured or designed to passsubstantially all of the pilot current between the power contact 206 andthe electrode body 202. The resilient conductive element 204 can beformed from a material that facilitates both carrying the electricalcurrent or load associated with initiating a pilot arc and dissipatingthermal heat associated with the current to prevent the resilientconductive element from melting during pilot arc operation. In someembodiments, the material of the resilient conductive element 204 isselected, for example, based on the current rating of the material. Insome embodiments, the resilient conductive element 204 is the path ofleast resistance and/or highest conductance between the power contact206 and the electrode body 202. Additionally, the mechanical propertiesof the resilient conductive element 206 facilitate movement of theelectrode body for contact starting the plasma arc torch. In someembodiments, the resilient element aids in aligning the electrode bodyrelative to the torch.

The resilient conductive element 204 can be an electrically conductivespring capable of reliably conducting about 31 amps of electric currentfor up to about 5 seconds or longer for pilot arc operation withoutmelting or otherwise changing the mechanical properties of the spring.In some embodiments, the resilient conductive element 204 is fabricatedfrom an alloy of Inconel® X-750. In some embodiments, the resilientconductive element 204 is fabricated from stainless steel. For example,the resilient conductive element 204 can be formed of 17/4 precipitationhardening stainless steel wire (conforming to AMS 5604 specifications)or Type 302 stainless steel wire (conforming to AMS 5866 or ASTM A 313specifications). In some embodiments, the resilient conductive element204 is formed from a wire of diameter about 0.762 mm (about 0.03 inches)and defines an outside diameter of about 7.62 mm (about 0.3 inches)300/1000 and a length along the longitudinal axis A of about 12.7 mm(e.g., about 0.5 inches).

In some embodiments, the resilient conductive element 204 is coated orplated with silver or a silver alloy to reduce electrical resistanceand/or improve electrical conductance. While depicted herein as ahelical compression spring, the resilient conductive element 204 caninclude other configurations, for example, a wave spring washer, afinger spring washer, curved spring washer, flat wire compression springof the crest-to-crest variety, or a slotted conical disk. For example,these types of springs are illustrated in U.S. Pat. No. 5,994,663assigned to Hypertherm, Inc., of Hanover, N.H., the contents of whichare hereby incorporated herein by reference. Other spring configurationsare also within the scope of the invention.

In some embodiments, the resilient conductive element 204 is a wiredisposed at the proximal end 210 of the electrode body 202, and a secondresilient element (not shown) is disposed at the distal end 212 of theelectrode body 202. The second resilient element biases the electrodebody toward the distal end 204 during pilot arc operation and restrainsradial motion of the electrode body 202 during torch operation (e.g.,during pilot arc operation and during workpiece processing). In thisway, the second resilient element aligns the electrode body 202 duringtorch operation.

FIG. 2C illustrates a cross section of the plasma arc torch of FIG. 2Bduring transferred arc mode. The contact surface 216 of the electrodebody 202 engages in substantially planar physical contact with thecorresponding surface 218 of the power contact 206 to establishelectrical communication (e.g., electrical current passes between theelectrode body 202 and the power contact 206 at the interface of thecontact surface 216 and the corresponding surface 218). When the contactsurface 216 of the electrode body 202 abuts the corresponding surface218 of the power contact 206, a current path is established such that acurrent passes directly between the power contact 206 and the electrodebody 202. In some embodiments, the resilient conductive element 204 nolonger carries a substantial amount of electrical current after theelectrode body 202 is moved into contact with the power contact 206. Insuch embodiments, the resilient conductive element 204 carrieselectrical current during initiation of the pilot arc, but not theentire duration of pilot arc operation. In some embodiments, theresilient conductive element 204 continues to carry electrical currentduring the entire duration of pilot arc operation.

When the arc has been transferred to the workpiece, a cutting current issupplied to the torch 240 (e.g., during transferred arc mode). In someembodiments, the resilient conductive element 204 does not carry asubstantial amount of electrical current during transferred arc mode.More particularly, the current path directly between the power contact206 and the electrode body 202 has lower resistance and/or higherconductance than the current path from the power contact 206 through theresilient conductive element 204 to the electrode body 202. The designillustrated in FIGS. 2A, 2B, and 2C combines dual functions, namelybiasing the electrode body 202 toward the nozzle 244 and providing anelectrical current path between the power contact 206 and the electrodebody 202, into a single component to reduce the number of consumablecomponents and to simplify torch design.

Previous torch designs, for example as disclosed in U.S. Pat. No.4,791,268, assigned to Hypertherm, Inc. of Hanover, N.H., employed aspring for providing a mechanical force to bias various torchcomponents. These torch designs also employed an electrical component(e.g., a non-resilient wire) for supplying electrical current for bothpilot arc operation and transferred arc operation. Such designs requiredthe wire, as the primary current path, to have a relatively largediameter to facilitate passing electrical current (e.g., up to 200 amps)during transferred arc operation without melting the wire.

In some embodiments, the resilient conductive element 204 is aconductive wire or metal strip for passing an electrical current betweenthe power contact 206 and the electrode body 202 during pilot arcoperation. When the electrode body 202 is in the blown-back state (e.g.,surface 216 of the electrode body 202 is in physical contact andelectrical communication with surface 218 of the power contact 206),substantially all of the electrical current for sustaining a plasma arcin transferred arc mode is passed directly between the surface 216 andthe surface 218. More specifically, the current path between the surface216 and the surface 218 when the surfaces 216, 218 are in physicalcontact can have a lower resistance and/or a higher conductivity thanthe resilient conductive element 202. Such a design employing a wireinstead of a spring as the resilient conductive element 204 permits awire having a smaller diameter and increased flexibility compared to theplunger wire of U.S. Pat. No. 4,791,268. A smaller wire is possiblebecause the resilient conductive element 204 of FIGS. 2A, 2B, and 2Cdoes not carry the full electrical current associated with transferredarc operation.

In some embodiments, the resilient conductive element 204 is aconductive sleeve in electrical communication with the power contact 206and the electrode body 202 for passing a pilot arc current therebetween.For example, such a sleeve can be designed to fit closely over theproximal end 210 of the electrode body 202 and over the portion 220 ofthe power contact 206. In some embodiments, a second resilient element(not shown), for example a spring, can be used in conjunction with asleeve to provide the mechanical function of biasing the electrode body202 toward the nozzle 244.

In some embodiments, both the power contact 206 and the resilientconductive element 204 are mounted to the torch body 242 and arerelatively secured with respect to the moveable electrode body 202. Forexample, when the nozzle 244 is removed from the torch body 242, theresilient conductive element 204 urges the electrode body 202 out of thetorch body 242 (e.g., the electrode body 202 is ejected), and thecurrent path between the resilient conductive element 204 and theelectrode body 202 is broken. In such an embodiment, the electrode body202 is a consumable component of the torch 240. In other embodiments,the combination of the electrode body 202 and the resilient conductiveelement 204 is a consumable component of the torch 240, e.g., the piecescan be sold or purchased together as a package.

FIG. 3A is a cross section of an exemplary embodiment of an electrodefor use in a contact start plasma arc torch. The electrode 300 includesan elongated electrode body 302 oriented along a longitudinal axis A.The electrode body 302 can be formed of an electrically conductivematerial such as tellurium copper, silver, silver copper alloys, orother alloys. The electrode body 302 includes a distal end 304 thatincludes a bore 306 for housing an emissive element (not shown) and aproximal end 308. The emissive element can be made from, for example,hafnium and is used to increase the operational life of a plasma arctorch (not shown) and to reduce wear on the electrode body 302. Duringoperation of the plasma arc torch and workpiece processing, the distalend 304 of the electrode body 302 is positioned near the workpiece (notshown), and the proximal end 308 is positioned remotely from theworkpiece. The electrode body 302 is movable along the longitudinal axisA when the electrode 300 is mounted within the torch.

The electrode 300 includes an electrically conductive resilient element310 (also referred to herein as the resilient conductive element 310).The resilient conductive element 310 is configured to pass substantiallyall of a pilot arc current between a power supply (not shown) and theelectrode body 302 during pilot arc operation. The resilient conductiveelement 310 is depicted as a helical spring that engages a radiallyextending flange 312 (e.g., a shoulder) disposed on the proximal end 306of the electrode body 302. The flange 312 can be a reaction surface forthe resilient conductive element 310. The physical contact between theresilient conductive element 310 and the flange 312 of the electrodebody 302 provides a current path.

In some embodiments, the resilient conductive element 310 is secured tothe flange 312 (e.g., by soldering or welding) such that the resilientconductive element 310 is retained by the electrode body 302. Theresilient conductive element 310 can be retained by a diametralinterference fit or other type of friction fit. In some embodiments, theresilient conductive element 310 is formed integrally with the electrodebody 302 (e.g., the electrode body 302 and the resilient conductingelement 310 are fabricated from the same piece of material). Theresilient conductive element 310 can be secured with respect to theelectrode body 302 to hinder disengagement of the resilient conductiveelement 310 from the electrode body 302 during processing or maintenanceoperations.

As illustrated, the electrode body 302 includes a series of fins 314that are formed integrally with the electrode body 302. The fins 314increase the surface area of the electrode body 302 and function as heattransfer surfaces to cool the electrode body 302 during torch operation.The fins 314 also form a type of seal that allows a plasma gasintroduced in the plasma chamber (e.g., the plasma chamber 254 of FIG.2B) to build sufficient gas pressure to move the electrode body 302longitudinally along axis A toward the proximal end 308. As discussedabove, movement of the electrode body 302 toward the proximal end 308initiates the pilot arc when a pilot arc current is passed between theresilient conductive element 310 and the electrode body 302.

The placement of the fins 314 provides a spiral groove axially along theelectrode body 302. Exemplary fins 314 are illustrated in U.S. Pat. No.4,902,871 assigned to Hypertherm, Inc. of Hanover, N.H., the contents ofwhich are hereby incorporated herein by reference. The fins 314 aredepicted as radially extending from the longitudinal axis A. Otherconfigurations of fins 314 are possible, for example, extendinglongitudinally along the axis A, such as illustrated in U.S. Pat. No.6,403,915 also assigned to Hypertherm, Inc. of Hanover N.H., thecontents of which are hereby incorporated herein by reference. Someembodiments of the electrode 300 do not include the fins 314, and thegas pressure exerts a force against a different surface of the electrodebody 302 to move the electrode body during initiation of a pilot arc.

The electrode 300 includes a contact element 316 that includes a firstsurface 318 and a second surface 320. The first surface 318 isconfigured for electrical communication with a power supply (not shown).For example, the first surface 318 can abut a corresponding surface of apower contact (e.g., the power contact 206 of FIG. 2A, not shown in FIG.3A). The power supply can provide electrical current to the contactelement 316 through the power contact. The second surface 320 isconfigured for electrical communication with a corresponding contactsurface 322 of the electrode body 302 after initiation of the pilot arcand during transferred arc mode. In some embodiments, the first surface318 of the contact element 316 is substantially stationary when theelectrode 300 is mounted within the torch (e.g., the first surface 318maintains physical engagement or contact with the power contact). Thecontact element 316 can be made from a relatively hard and electricallyconductive material, for example, stainless steel, chromium copper,nickel, or beryllium copper. In some embodiments, the contact element316 is made from a material harder than the material that forms theelectrode body 302. In some embodiments, the contact element 316 iscoated with a relatively hard and electrically conductive material.

As depicted, the resilient conductive element 310 circumscribes theproximal end 308 of the electrode body 302 and engages the secondsurface 320 of the contact element 316. Other configurations forproviding a current path from the contact element 316 through theresilient conductive element 310 to the electrode body 302 are withinthe scope of the invention. In some embodiments, a second conductiveelement (not shown) provides a current path between the contact element316 and the electrode body 302 having lower resistance and/or higherconductivity than the resilient conductive element 310. In suchembodiments, the resilient conductive element 310 biases the electrodebody away from the contact element 316 (e.g., performs a mechanicalfunction) but does not carry a substantial amount of pilot current. Insome embodiments, the resilient conductive element 310 is secured to thecontact element 316 (e.g., by soldering or welding) or formed integrallywith the contact element 316. In some embodiments, the resilientconductive element 310 can be disposed between the second surface 320 ofthe contact element 316 and the corresponding contact surface 322 of theelectrode body. In some embodiments, the first surface 318 of thecontact element 316 engages the resilient conductive element 310.

The illustrated electrode body 302 includes a receptacle 324 disposed atthe proximal end 308 of the electrode body 302 and separated from thebore 306 at the distal end 304 by the electrode body 302 (e.g., neitherthe bore 306 nor the receptacle 324 is a through-hole). In someembodiments, the receptacle 324 is substantially aligned with the axis Aand defines an inner surface 326. The contact element 316 includes aconnective member 328 that extends from the second surface 320. In someembodiments, the connective member 328 slideably engages the electrodebody 302. For example, the connective member 328 includes an aligningportion 330 that is substantially coaxial with the longitudinal axis A.The aligning portion 330 can slideably engage the inner surface 326 ofthe receptacle 324. In some embodiments, the engagement between thealigning portion 330 and the inner surface 326 restrains radial motionof the electrode body 302 or the contact element 316 within the torch.

The receptacle 324 can be configured to hinder disengagement of thecontact element 316 from the electrode body 302. The electrode body 302includes a restraint surface 332 disposed at the proximal end of thereceptacle 324 for reacting against a portion of the contact element 316to hinder disengagement. In some embodiments, the restraint surface 332reacts against the connective member 328 or the aligning portion 330 ofthe contact element 316 (e.g., by a diametral interference fit). In someembodiments, the restraint surface 332 includes an annular or ring-likeconfiguration. The restraint surface 332 can be disposed within thereceptacle 324 such that the restraint surface does not interfere withor prevent the second surface 320 of the contact element 316 fromphysically contacting the contact surface 322 of the electrode body 302in a substantially planar manner.

In some embodiments, the first surface 318, the second surface 320, orboth can be coated with silver or a silver alloy to improve theelectrical current flow between the power supply and the electrode body302 (e.g., by reducing the electrical resistance at the surfaces 318 and320 of the contact element 316. In some embodiments, the slideableengagement between the contact element 316 and the electrode body 302provides a current path of lower resistance and/or higher conductivitythan the resilient conductive element 310. In such embodiments, theresilient conductive element 310 biases the electrode body away from thecontact element 316 (e.g., performs a mechanical function) but does notcarry a substantial amount of pilot current. More specifically, theconnective member 328 or the aligning portion 330 can be fabricated torelatively tight tolerances sufficient to form a low-resistance path forelectrical current to pass to the electrode body 302, for example, viathe receptacle 324. Relatively tight tolerances are required to preventionization or formation of an arc in the space between the connectivemember 328 or aligning portion 330 and the receptacle 324.

FIG. 3B is a more detailed illustration of the components of theelectrode of FIG. 3A prior to assembly. FIG. 3B illustrates a close-upview of the proximal end 308 of the electrode body 302. In theillustrated embodiment, the electrode body 302, resilient conductiveelement 310, and the contact element 316 do not form an integralassembly. More particularly, the contact element 316 (e.g., theconnective member 128 and aligning portion 130) can be freely disengagedfrom the resilient conductive element 310 and the electrode body 302(e.g., the receptacle 324). In some embodiments, the length of theconnective member 328 and the aligning portion 330 does not exceed thedepth of the receptacle 324 such that the contact element does not“bottom out” against the bottom surface 334 of the receptacle 324.

The proximal end 308 of the electrode body 302 can define a lip 336adjacent the receptacle 324 that extends axially along the longitudinalaxis A. The lip 336 can be formed from the same piece of material as theelectrode body 302. In some embodiments, the contact element 316 may beretained with respect to the electrode body 302 (e.g., a portion of theelectrode body 302 hinders disengagement of the contact element 316 fromthe electrode body 302). For example, the connective member 328 and thealigning portion 330 can be positioned within the receptacle 324. Thecontact element 316 is pressed against the electrode body 302 such thatthe second surface 320 of the contact element 316 engages the lip 336 asthe second surface 320 advances into physical contact with the contactsurface 322 of the electrode body 302.

The engagement between the second surface 320 and the lip 336 deformsthe lip 336 into the adjacent receptacle 324 to enable facing physicalcontact between the second surface 320 of the contact element 318 andthe contact surface 322 of the electrode body 302. The deformed lip 336can form the restraint surface 332 of FIG. 3A. In some embodiments, thecontact element 316 is pressed against the electrode body 302 at thesame time the emissive element is disposed within the bore 306. Forexample, during a process known as swaging, a force along thelongitudinal axis A (e.g., toward the proximal end 308 of the electrodebody 302) is applied with respect to the emissive element to secure theemissive element within the bore 306. During swaging, anoppositely-oriented force (e.g., toward the distal end 304 of theelectrode body 302) is applied to press the contact element 316 againstthe proximal end 308 of the electrode body 302 to deform the lip 336. Insome embodiments, the applied force is about 4,450 N of force (e.g.,approximately 1000 lbs. of force). In some embodiments, after swaging,the restraint surface 332 can withstand about 356 N of force (e.g.,about 80 lbs. of force) before failing (e.g., permitting the contactelement 316 to be disengaged from the electrode body 302).

In some embodiments, the resilient conductive element 310 is disposedbetween the electrode body 302 (e.g., in physical contact with theflange 312) and the contact element 316 (e.g., in physical contact withthe second surface 320) prior to deforming the lip 336. The resilientconductive element 310 can be “captured” between the contact element 316and the electrode body 302. The restraint surface 332 can hinderdisengagement of the slideably mounted contact element 316 from theelectrode body 302. In some embodiments, the electrode 300 is assembledprior to use within a plasma arc torch and can be packaged as anintegral assembly.

In some embodiments, the restraint surface 332 has an annularconfiguration (e.g., when the lip 336 axially extends along thelongitudinal axis A about the circumference of the receptacle 324). Inother embodiments, the restraint surface 332 is formed along a portionof the circumference of the receptacle 324 less than the entirecircumference. The connective member 328 or the aligning portion 330 canbe freely inserted into the receptacle 324 without interference with therestraint surface 336, but, e.g., rotating the contact element 316 aboutthe longitudinal axis A hinders disengagement of the contact element 316by establishing interference between the restraint surface 332 and theconnective member or the aligning portion 330.

FIG. 4A depicts a cross section of an exemplary contact start plasma arctorch. The configuration of FIG. 4A can be referred to as the “forward”configuration or the “start” configuration. The torch 400 includes atorch body 402 that defines a gas inlet 404. The torch 400 includes apower contact 406 in electrical communication with a power supply (notshown) that provides an electrical current to the power contact 406. Thetorch 400 includes the electrode 300 of FIG. 3A. The first surface 318of the contact element 316 is configured for physical contact andelectrical communication with the power contact 406. The resilientconductive element 310 urges the electrode body 302 away from the powercontact 406 and into physical contact and electrical communication witha nozzle 408. The electrode body 302 (e.g., the distal end 304 of theelectrode body 302) cooperates with the nozzle 408 to form a portion ofa plasma chamber 410. The nozzle 408 includes an exit orifice 412 thatpermits the plasma arc or jet (not shown) to exit the plasma chamber 410for transferring to a workpiece (not shown). A shield 414 is mounted toa retaining cap 416 that is mounted on a portion 418 of the torch body402. The shield 414 includes an exit port 420 that is adjacent the exitorifice 412 of the nozzle 408. The exit port 420 permits the plasma jetto be transferred from the torch 400 to the workpiece. The shield 414prevents material that is spattered during workpiece processing fromaccumulating on the nozzle 408 and reducing the useful life of thenozzle 408 or the electrode 300. The torch 400 also includes a swirlring 422 that defines one or more ports 424 that permit a gas (notshown) to flow into and out of the plasma chamber 410.

Pilot arc operation begins with initiation of a pilot arc. A pilotcurrent is passed between the power supply and the power contact 406.The power contact 406 passes the pilot current to the contact element316 across the interface between the power contact 406 and the firstsurface 318 of the contact element 316. The pilot current passes betweenthe contact element 316 (e.g., the second surface 320) and the resilientconductive element 310. The current then passes between the resilientconductive element 310 and the electrode body 302 and the nozzle 408. Anexemplary current suitable for use as a pilot arc current is betweenabout 22 and 31 amps. In some embodiments, the power contact 406 isfabricated from tellurium copper, brass, copper, or other materialssuitable for passing current both during pilot arc operation andtransferred arc operation.

During pilot arc operation, gas enters the torch 400 through the inlet404 defined by the torch body 402. The gas is directed along apassageway 426 defined by the torch body 402. The swirl ring 422 definesone or more channels 428 that allow the gas to pass from the passageway426 to a space 430 defined by the exterior of the swirl ring 422 and theportion 418. The gas flows through the ports 424 into the plasma chamber410. Gas pressure in the plasma chamber 410 builds until the pressure issufficient to overcome the force provided by the resilient conductiveelement 310 and move the electrode body 302 away from the nozzle 408thereby creating a space or gap between the electrode body 302 and thenozzle 408. In some embodiments, gas in the plasma chamber 410 acts onthe fins 314 of the electrode body 302, exerting a pressure along thelongitudinal axis A toward the proximal end 310 of the electrode body302. The electrode body 302 moves with respect to the torch 400substantially along the longitudinal axis A. In some embodiments, thecontact element 316 aligns the electrode body 302 by restraining radialmotion of the electrode body 302 both during pilot arc operation andduring transferred arc mode. As the electrode body 302 is moved awayfrom the nozzle 408, a relative electric potential develops between theelectrode body 302 and the nozzle 408. The potential difference causesan arc (not shown) to be generated in the now present gap between theelectrode body 302 and the nozzle 408 (e.g., by ionizing a path of leastresistance between the electrode body 302 and the nozzle 408). The arcionizes the gas in the plasma chamber 310 to form the plasma jet used inworkpiece processing.

FIG. 4B illustrates a cross section the plasma arc torch of FIG. 4Aincluding illustrative components after pilot arc initiation. Theconfiguration of FIG. 4B can be referred to as the “blown-back”configuration because the electrode body 302 has been separated from thenozzle 408. The electrode body 302 is moved along the axis A until thecontact surface 322 of the electrode body 302 contacts the secondsurface 320 of the contact element 316. The first surface 318 of thecontact element 316 maintains physical contact and electricalcommunication with the power contact 406 that is relatively stationarywith respect to the electrode body 302. In some embodiments, theduration of time during which the electrode body 302 moves along theaxis A is less than or equal to about 0.3 seconds. In some embodiments,the resilient conductive element 310 carries electrical current in theblown-back configuration (e.g., during pilot arc operation after pilotarc initiation). In some embodiments, the resilient conductive element310 carries electrical current only during pilot arc initiation.

In general, the arc is transferred from the nozzle 408 to the workpiece(not shown) for workpiece processing by positioning the torch 400 nearthe workpiece. The workpiece is maintained at a relatively lowerelectric potential than the nozzle 408. In some embodiments, the arc istransferred during pilot arc initiation (e.g., before the blown-backconfiguration of FIG. 4B). An electrical lead (not shown) incommunication with the workpiece can provide a signal to the powersupply (not shown) based on the transfer of the arc to the workpiece.When the electrode body 302 is in the blown-back configuration, thepower supply provides an increased electrical current (e.g., a cuttingcurrent) to the torch 400. One example of a method for increasing theelectrical current to the torch is known as “dual-threshold” and isdescribed in U.S. Pat. No. 6,133,543 and assigned to Hypertherm, Inc. ofHanover, N.H., the disclosure of which is hereby incorporated herein byreference.

The cutting current can be, for example, approximately 100 toapproximately 150 amps. The cutting current is associated with operationof the torch 400 in transferred arc mode. In some embodiments, theamount of cutting current that is provided is dependent on thecomposition of the workpiece or on physical properties of the workpiece(e.g., thickness of the workpiece or the depth of a cut). In someembodiments, transferred arc mode refers to both the arc beingtransferred to the workpiece and the power supply providing the cuttingcurrent. In other embodiments, transferred arc mode refers to the arcbeing transferred to the workpiece.

When the electrode body 302 is in the blown-back configuration, thepower supply provides electrical current to the power contact 406, tothe contact element 316, and to the electrode body 302. The contactelement 316 remains relatively stationary with respect to the electrodebody 302 and power contact 406. More particularly, the first surface 318of the contact element 316 can be designed to remain in physical contactand electrical communication with the power contact 406 after theelectrode 300 is installed in the torch 400. In some embodiments, thecontact element 316 is secured relative to the power contact 406, forexample by a friction fit, e.g., such that the earth's gravitationalforce acting on the electrode body 302 is insufficient to remove theelectrode 300 from the torch 400. Most of the wear on the electrode 300occurs at the interface between the second surface 320 of the contactelement 316 and the contact surface 322 of the electrode body 302 due tothe repeated contact and separation of the electrode body 302 and thecontact element 316 during operation (e.g., starting and stopping) ofthe torch 400. The design of the electrode 300 reduces the amount ofwear on the power contact 406 because the first surface 318 of thecontact element 316 remains in contact with the power contact 406 toreduce the formation of an arc between the power contact 406 and thefirst surface 318. Formation of an arc between the power contact 406 andthe first surface 318 can create surface imperfections that reduce theoperational life of the power contact 406 and the electrode 300.

FIG. 5A depicts a cross section of an exemplary electrode including acontact element and a resilient conducting element disposed within areceptacle of the electrode body. The electrode 500 includes anelectrode body 502 defining a distal end 504 and a proximal end 506oppositely disposed along the longitudinal axis A. The distal end 504defines a bore 508 for receiving an emissive element 510. The proximalend 506 of the electrode body 502 defines a receptacle 512 in acylindrical configuration centered about the longitudinal axis A. Insome embodiments, a non-cylindrical configuration for the receptacle 512can be used. The receptacle 512 is separated from the bore 508 by theelectrode body 502 (e.g., the electrode body 502 does not have athrough-hole). The receptacle 512 defines a first contact surface 514disposed at the bottom of the receptacle 512. The contact surface 514 isconfigured for electrical communication and/or physical contact with apower contact (depicted in FIG. 5B). The receptacle 512 also defines asecond contact surface 516.

The electrode 500 includes a contact element 518 and a resilientconductive element 520 that are disposed within the receptacle 512. Thecontact element 518 defines a first surface 522 and a second surface524. The second surface 524 is configured to react against the resilientconductive element 520 and against the second contact surface 516 of thereceptacle 512. The resilient conductive element 520 reacts against thefirst contact surface 514 to urge the electrode body 502 into abuttingrelation with a nozzle (not shown) when installed within a plasma torch.In some embodiments, the resilient conductive element 520 can reactagainst a third surface (not shown) within the receptacle 512.

The contact element 518 defines an annular configuration designed tosurround a power contact. The annular configuration provides an aligningportion 526 to restrain radial motion of the electrode body 502 byreacting against the power contact. The contact element 518 andresilient conductive element 520 are retained with respect to thereceptacle 512 by a tapered portion 528 of smaller diameter than thediameter of the contact element 518. In some embodiments, the taperedportion 528 is a restraint surface that hinders disengagement of thecontact element 518 and the resilient conductive element 520 fromdisengaging the electrode body 502 (e.g., the receptacle 512). Forexample, the combination of the tapered portion 528 and the contactelement 518 hinder the resilient conductive element 520 from disengagingthe electrode body 502 by a diametral interference fit. In someembodiments, the tapered portion 528 defines an annular configuration.In some embodiments, the receptacle 512 does not include a taperedportion 528, and the contact element 518 and the resilient conductiveelement 520 are not retained with respect to the receptacle 512.

FIG. 5B depicts the electrode of FIG. 5A disposed in a transferred arcmode. FIG. 5B illustrates a close-up of a cross-section of the proximalend 506 of the electrode body 502 and a power contact 540. The powercontact 540 defines an axially extending portion 542 configured tointeract with the receptacle 512 and the contact element of theelectrode 500. The axially extending portion 542 defines a firstcorresponding surface 544 and a second corresponding surface 546 forelectrical communication and/or physical contact with the first contactsurface 514 of the electrode body 502 (e.g., as defined by thereceptacle 512) and the first surface 522 of the contact element 518,respectively. The power contact 540 also defines a seat portion 548configured to correspond to the tapered portion 528 of the electrodebody 502 to restrain radial motion of the electrode body 502.

In some embodiments, the electrode 500 is positioned within a torch suchthat the first surface 522 of the contact element 518 is in electricalcommunication and/or physical contact with the second correspondingsurface 546 of the power contact 540 to form an interface that remainsrelatively stationary with respect to the electrode body 502 duringtorch operation. The second surface 524 of the contact element 518 isinitially remote from the second contact surface 516 of the receptacle512, and the first corresponding surface 544 of the power contact isremote from the contact surface 514 of the electrode body 502.

During pilot arc operation, a pilot current passes between the powersupply (not shown) and the power contact 540. The pilot current passesfrom the power contact 540 to the contact element 518 and from thecontact element 518 through the resilient conductive element 520 to theelectrode body 502, such that the resilient conductive element 518carries substantially the entire pilot arc current. As the electrodebody 502 is moved away from the nozzle (not shown) to generate an arc,the second contact surface 516 moves into contact with the secondsurface 524 of the contact element 516, and the first contact surface514 moves into contact with the first corresponding surface 544 of thepower contact 540. Substantially all of the cutting current is passedfrom the power contact 540 through the contact element 516 to theelectrode body 502 and directly to the electrode body. Duringtransferred arc operation, the resilient conductive element 520 does notcarry a substantial amount of current.

In some embodiments, the first corresponding surface 544 or the secondcorresponding surface 546 pass substantially all of the electricalcurrent during transferred arc operation to the electrode body 502.Multiple corresponding surfaces 544, 546 can reduce physical wear on thefirst contact surface 514 of the electrode body 502 or the first surface522 of the contact element 518. Such a configuration results in reducedwear by reducing the mechanical load associated with physical contactbetween the power contact 540 and each of the contact element 518 andthe electrode body 502. Reduced wear can prolong the life of theelectrode 500.

FIG. 6A depicts a cross section of an exemplary electrode including acontact element and resilient conducting element disposed at a proximalend of the electrode body. The electrode 600 includes an electrode body602 defining a distal end 604 and a proximal end 606 oppositely disposedalong the longitudinal axis A. The distal end 604 defines a bore 608 forreceiving an emissive element 610. The electrode 600 includes a contactelement 612 and a resilient conductive element 614. The contact element612 defines a first contact surface 616 configured for electricalcommunication and/or physical contact with a power contact (see FIG. 6B)and a second contact surface 618 for electrical communication and/orphysical contact with a corresponding surface 620 of the electrode body602. The proximal end 606 of the electrode body 602 defines a contactsurface 622 for electrical communication and/or physical contact withthe power contact. The electrode body 602 defines a reaction surface 624for reacting against the resilient conductive element 614 to provide abiasing force against the reaction surface 624 and the electrode body602. The proximal end 606 of the electrode body 602 defines a firstrestraint surface 626 for hindering disengagement of the contact element612 and the resilient conductive element 614 (e.g., by a diametralinterference fit). In some embodiments, the electrode body 602 does notinclude the restraint surface 624, and the contact element 612 and/orthe resilient conductive element 614 are disengageable with respect tothe electrode body 602. In some embodiments, the resilient conductiveelement 614 is secured to one of the electrode body 602 or the contactelement 612 or both.

The contact element 614 defines an annular configuration and includes analigning portion 628 that restrains radial motion of the electrode body602. For example, the aligning portion 628 can interact with an axiallyextensible portion 630 of the proximal end 606 of the electrode body602. The portion 630 defines a diameter slightly less than the diameterof the aligning portion 628 such that the portion 630 can slidinglyengage the aligning portion 628 along the longitudinal axis A without asignificant radial perturbation.

FIG. 6B depicts the electrode of FIG. 6A disposed in a transferred arcmode. The configuration of FIG. 6B includes a power contact 640positioned relative to the proximal end 606 of the electrode body 602.The power contact 640 defines an opening 642 into which the proximal end606 of the electrode body 602 advances as the electrode body 602 movesaway from the nozzle (not shown) under gas pressure. The opening 642 isadjacent a receptacle portion 644 that is substantially centered aboutthe longitudinal axis A. The receptacle portion 644 defines a firstcontact surface 646 for electrical communication and/or physical contactwith the contact element 612 and a second contact surface 648 forelectrical communication and/or physical contact with the contactsurface 622 of the electrode body 602. The receptacle portion 644 isdimensioned to receive the contact element 612 and the resilientconductive element 614 in addition to a portion of the proximal end 606of the electrode body 602. In some embodiments, the receptacle portion644 is dimensioned to only receive the proximal end 606 of the electrodebody 602.

During installation, the electrode 600 is positioned such that the firstsurface 616 is in electrical communication and/or physical contact withthe first contact surface 646 of the power contact 640 to form aninterface that is relatively stationary with respect to the electrodebody 602 during torch operation. The second surface 618 of the contactelement 612 is initially physically remote from the correspondingsurface 620 of the electrode body, and the contact surface 622 of theelectrode body 602 is initially physically remote from the secondcontact surface 648 of the power contact 640.

During pilot arc operation, a pilot current passes between the powersupply (not shown) and the power contact 640. The pilot current passesfrom the power contact 640 to the contact element 612 and from thecontact element 612 through the resilient conductive element 614 to theelectrode body 602, such that the resilient conductive element 614carries substantially the entire pilot arc current. As the electrodebody 602 is moved away from the nozzle (not shown) to generate an arc,the corresponding surface 620 moves into electrical communication and/orphysical contact with the second surface 618 of the contact element 612,and the contact surface 622 moves into electrical communication and/orphysical contact with the second contact surface 648 of the powercontact. Substantially all of the cutting current is passed from thepower contact 640 through the contact element 612 to the electrode body602 and directly to the electrode body 602. During transferred arcoperation, the resilient conductive element 614 does not carry asubstantial amount of the current.

In some embodiments, the first corresponding surface 646 or the secondcorresponding surface 648 pass substantially all of the electricalcurrent during transferred arc operation to the electrode body 602.Multiple corresponding surfaces 646, 648 can reduce physical wear on thefirst contact surface 622 of the electrode body 602 or the first contactsurface 616 of the contact element 612. Such a configuration results inreduced wear by reducing the mechanical load associated with physicalcontact between the power contact 640 and each of the contact element612 and the electrode body 602. Reduced wear can prolong the life of theelectrode 600.

FIG. 7A depicts a partially exploded view of an exemplary contactelement, resilient element, and power contact that embody principles ofthe invention. The two-piece power connection 700 includes a powercontact 702, a contact element 704, and a resilient element 706,substantially aligned along the longitudinal axis A. The power contact702 defines an aperture 708 adjacent a cavity 710 for receiving anaxially extensive portion 712 of the contact element 704. The diameterof the portion 712 is slightly smaller than the diameter of the cavity710. A second resilient element 714 is radially dimensioned along anaxial extent of the portion 712 to provide sufficient friction withrespect to the cavity 710 to hinder the portion 712 and the contactelement 704 from disengaging the power contact 702 (e.g., a frictionfit) and to restrain radial motion of the contact element 704. In someembodiments, the second resilient element 714 is a Louvertac™ spring,for example, fabricated with beryllium copper and sold by TycoElectronics Corp., of Harrisburg, Pa. Other copper alloys are alsowithin the scope of the invention. In some embodiments, the secondresilient element 714 is plated with a conductive metal, for example,gold, silver, nickel or tin. In some embodiments, the second resilientelement 714 is electrically conductive and passes a portion of theelectrical current supplied by a power supply (not shown) between thepower contact 702 and the contact element 704. The resilient element 706can pass a pilot arc current between the power supply and the electrodebody during initiation of a pilot arc.

The power contact 702 defines a surface 716 adjacent the aperture 708for passing electrical current to a first corresponding surface 718 ofthe contact element 704 where the first surface 718 is adjacent theextensive portion 712. The contact element 704 also includes a secondsurface 720 opposite the first surface 718 for reacting against thefirst resilient element 706. The contact element 704 includes a portion722 axially protruding from the second surface 720 and defines a smallerdiameter than an inside diameter of the resilient element 706 such thatthe resilient element 706 surrounds the portion 722. The portion 722 isconfigured for electrical communication with a proximal end of a torchelectrode body (not shown). The portion 722 defines a perimeter surface724 and an end surface 726. In some embodiments, the perimeter surface724, the end surface 726, or both engage corresponding surfaces of theelectrode body. The resilient element 706 is coupled to a component 728.The component 728 is designed for reacting against a correspondingsurface (not shown) of the electrode body to provide an axial forcedirected toward the distal end (not shown) of the electrode body (e.g.,away from the power contact 700). Gas pressure reacts against a gasreaction surface of the electrode body and overcomes the axial force tomove the electrode body axially toward the proximal end until theperimeter surface 724, the end surface 726 or both react againstcorresponding portions of the electrode body during transferred arcoperation.

In some embodiments, the component 728 is formed integrally and of thesame material as the resilient element 706. In some embodiments, thecomponent 728 is a separate component and/or formed from a differentmaterial that is secured to the resilient element 706. The component 728is depicted as an annular washer coupled to the resilient element 706.Other configurations of the component 728 can be used, for example, acircular plate or a thimble design that circumscribes an adjacent axialouter portion of the resilient element 706 (e.g., a design similar tothe contact element 904 discussed below with respect to FIG. 9). Suchconfigurations permit the resilient element 706 to be hidden from theperspective of the electrode body, such that the electrode body and thecomponent 728 move substantially together relative to the power contact702. More specifically, the component 728 is stationary relative to theelectrode body and movable relative to the contact element 704 and thepower contact 702.

In some embodiments, a first surface (not shown) of the component 728faces a corresponding surface of the electrode body and a second surface(not shown) of the component 728 faces the end surface 726 of thecontact element 704. During transferred arc operation, the secondsurface of the component 728 is in physical contact with the end surface726 of the contact element 704, and the first surface of the component728 is in physical contact with the electrode body to provide anelectrical current path from the power supply to the electrode bodythrough the power contact 702 and the contact element 704.

In some embodiments, the resilient element 706 is not electricallyconductive, and a conductive element (not shown) provides an electricalcurrent path to the component 728 during pilot arc operation. Theconductive element can be a wire or a conductive strip positioned toelectrically connect the component to the contact element 704 or thepower contact 702, for example, by soldering, welding or otherwiseestablishing electrical contact between the contact element 704 or thepower contact 702 and the conductive element.

During transferred arc operation, a transferred arc current can bepassed via physical contact between the contact element 704 (e.g., viathe perimeter surface 724, the end surface 726, or both) and theelectrode body. Such a configuration allows a conductive element with arelatively low current rating to be used to pass the pilot current tothe electrode body, which allows a relatively small conductive elementto be used. A small conductive element is beneficial to reduce physicalinterference between the conductive element and the moving parts of thetorch system (e.g., the resilient element 706 and the electrode body).Substantially all of the operating current (e.g., pilot current andtransferred arc current) is passed to the electrode body via thecomponent 728.

FIG. 7B depicts the components of FIG. 7A disposed in a plasma arc torchoperation. The portion 712 of the contact element 704 is advanced intothe cavity 710, and the second resilient element 714 reacts against aninside surface (not shown) of the cavity 710 to hinder disengagement ofthe contact element 704 using friction. The first corresponding surface718 of the contact element 704 seats against or is in physical contactwith the surface 716 adjacent the cavity 710 to provide a current pathfrom the power contact 702 to the contact element 704. In someembodiments, the contact element 704 or the resilient element 706 can bereplaced without replacing the power contact 702. Because the interfacebetween the power contact 702 and the contact element 704 (e.g., theinterface between the surface 716 and the corresponding surface 718) isstationary relative to the power contact 702, the power contact 702 doesnot wear as quickly as in configurations in which the current path andthe physical interface coincide. In some embodiments, the contactelement 704, and the power contact 702 can form a unitary body (e.g.,fabricated from the same piece of material) rather than as two separatepieces. The configuration of FIGS. 7A and 7B can be employed in existingcontact start plasma arc torches, for example, as shown in FIG. 1, byreplacing the unitary power contact 108 with the two-piece powerconnection 700 and by replacing the cathode block 116 to facilitate thepower connection 700. The power connection 700 can be fastenedrelatively stationary with respect to the electrode body, for example,by a clip or a pin as discussed above.

FIG. 8A depicts a cross section of another embodiment of an electrodebody, resilient conductive element, and contact element prior toinstallation within a plasma arc torch. The electrode 800 includes anelectrode body 802, a contact element 804 and a resilient conductiveelement 806 substantially aligned with respect to the longitudinal axisA. FIG. 8A illustrates a proximal end 808 of the electrode 800 that canbe disposed within a plasma arc torch body (not shown). The electrodebody 802 features a shoulder 810 that extends radially from theelectrode body 802. The shoulder 810 defines a first surface 812 and asecond surface 814. In some embodiments, the first surface 812 acts as arestraint surface configured to contact a corresponding surface 816 ofthe contact element 804 and prevent disengagement of the contact element804 from the electrode body 802 in the presence of an axially directedforce (e.g., provided by the resilient conductive element 806, gaspressure, or in some cases gravity). The second surface 814 of theshoulder 810 is configured to engage a surface 818 of the resilientconductive element 806 to form a reaction interface.

The contact element 804 defines a first surface 820 and a second surface822. The first surface 820 is designed or configured to seat against ormate with a corresponding surface (not shown) of a power contact (notshown) to establish physical contact and electrical communication. Thesecond surface 822 of the contact element 804 is designed or configuredto correspond a surface 826 defined by the electrode body 802. In someembodiments, the resilient conductive element 806 engages the secondsurface 822 of the contact element 804 to provide axially directedforces. The contact element 804 defines a receptacle 828. The receptacle828 is sized to allow the resilient conductive element 806 to bedisposed about a portion 830 of the electrode body 802 and disposedwithin the receptacle 828 of the contact element.

In some embodiments, during pilot arc operation, the first surface 820of the contact element 804 is in electrical communication (and/orphysical contact) with the power contact. The power contact provides anelectrical current to the first surface 820 that is transferred acrossthe contact element 804 to the second surface 822. Current can passbetween the contact element 804 and the resilient conductive element 806via the interface between the resilient conductive element 806 and thesecond surface 822. The resilient conductive element 806 provides acurrent path for passing current between the power contact and theelectrode body 802. For example, current passes between the electrodebody 802 and the resilient conductive element 806 at the interfacebetween the surface 818 and the corresponding second surface 814 of theshoulder 810. In general, the receptacle 828, the resilient conductiveelement 806 and/or the surface 812 cooperate to restrain radial motionof the electrode body 802 when the electrode 800 is mounted with theplasma arc torch.

FIG. 8B illustrates the configuration of the components of FIG. 8Aduring transferred arc mode. During pilot arc mode, gas pressure reactsagainst the electrode body 802 to overcome the urging of the resilientconductive element 806 in a direction axially away from the proximal end808 to move the electrode body 802, specifically the surface 826 intocontact with the corresponding second surface 822 of the contact element804. In this configuration, electrical communication can be establisheddirectly between the contact element 804 and the electrode body 802, andthe electrical current can be increased for transferred arc operation.In some embodiments, the contact element 804 defines an end surface 840that is remote from a surface 842 of the electrode body 802. In someembodiments, the end surface 840 contacts or “bottoms out” by reactingagainst the surface 842 to provide a second current path between thecontact element 804 and the electrode body 802.

FIG. 9 depicts a cross section of another embodiment of an electrodethat embodies the invention. The electrode 900 includes an electrodebody 902, a contact element 904 and a resilient conductive element 906substantially aligned along the longitudinal axis A. The electrode body902 defines a radially extending surface 908 that can react against asurface 910 of the resilient conductive element 906 to hinderdisengagement (e.g., capture) of the resilient conductive element 906from the electrode body 902. The resilient conductive element 906 or thesurface 910 can be advanced axially along the longitudinal axis A andforced or pressed over the surface 908 to form a diametral interferencefit. Other types of fits may be used to hinder disengagement of theresilient conductive element 906 from the electrode body 902.

The contact element 904 defines a receptacle 912, a first surface 914for electrical communication and/or physical contact with acorresponding surface of a power contact of a plasma arc torch (notshown), and a second surface 916 for electrical communication and/orphysical contact with a corresponding surface 918 of the electrode body902. The receptacle 912 can be dimensioned such that an inside diameterof the receptacle is slightly less than an outside diameter of theresilient conductive element 906. The contact element 904 and thereceptacle 912 can be pressed or forced over the resilient conductiveelement 906 to establish a friction or other type of fit between aportion of the resilient conductive element 906 and the receptacle 912.In some embodiments, alternative or additional joints or fits can beused to secure the contact element 904 to the resilient conductiveelement 906 and the electrode 900. In general, the receptacle 912cooperates with the resilient conductive element 906 to radiallyrestrain the electrode body 902 when the electrode 900 is mounted withinthe plasma arc torch.

FIG. 10A is a perspective view of an exemplary contact element andresilient conductive element that embody principles of the invention.The system 1000 includes a contact element 1002 and a resilientconductive element 1004 disposed within a receptacle 1006 of the contactelement 1002. The contact element 1002 includes a flange 1008 thatdefines one or more through-holes 1010 to facilitate gas passage aboutthe system 1000. In some embodiments, the through-holes 1010 impart aswirling motion to gas as the gas moves about an electrode body, forexample, to cool the electrode body or a plasma arc torch. In someembodiments, the resilient conductive element 1004 is secured orfastened (e.g., by bonding) to the contact element 1002. In someembodiments, the resilient conductive element 1004 is formed integrallywith the contact element 1002.

FIG. 10B is a cross-sectional view of a portion of a plasma arc torchemploying the components of FIG. 10A during pilot arc operation. Thetorch 1020 includes the contact element 1002, the resilient conductiveelement 1004, an electrode body 1022, and a power contact 1024substantially aligned along the longitudinal axis A. In someembodiments, the power contact 1024 is in electrical communication witha power supply (not shown). The power contact 1024 is surrounded by atorch component 1026 that cooperates with an exterior surface 1028 ofthe contact element 1004 to define a gas passageway 1030. Gas can besupplied for generating the plasma arc and for workpiece processing asdiscussed above with respect to FIG. 2A. Gas pressure within the torch1020 is relieved by flowing around the electrode body 1022 (e.g., byswirling around the electrode body 1022 guided by the fins 1032) towardsthe power contact 1024. Gas can flow through the holes 1010 in thecontact element 1004 and along the gas passageway 1030 away from theelectrode body 1022.

In the illustrated embodiment, the flange 1008 is disposed between asurface 1034 of the torch component 1026 and a surface 1036 of the swirlring 1038. In some embodiments, the system 1000 of FIG. 10A is aconsumable component and is installed within the torch 1020, and theelectrode body 1022 is replaced more frequently than the system 1000.This allows, for example, the electrode body 1022 to be consumed andchanged easily and without disassembling the torch 1020. In someembodiments, the system 1000 is secured with respect to the powercontact 1024 by an interference fit. For example, the system 1000 islocated within the torch 1020, and the swirl ring 1038 is secured (e.g.,by threading) relative to an outside surface 1040 of the torch component1026 to axially and/or radially secure the flange 1008 with respect tothe torch component 1026, power contact 1024 and/or the torch 1020. Insome embodiments, the flange reacts with or seats against othercomponents of the torch 1020.

One or more components of the system 1000 can be integrated with theswirl ring 1038. For example, the flange 1008 can be bonded or otherwisesecured to the swirl ring 1038 to form a unitary component. In someembodiments, the contact element 1002 is formed of the same material asthe swirl ring 1038 during the machining or manufacturing process. Theresilient element 1004 can be secured to the contact element 1002-swirlring 1038 combination, for example by a diametral interference fit orother securing methods. In some embodiments, the resilient element 1004is not secured to either the contact element 1002 or the swirl ring1038.

The electrode body 1022 can be moved (e.g., by gas pressure) towards thepower contact 1024 such that a surface 1042 of the electrode body 1022engages a corresponding surface 1044 of the contact element 1002 toestablish electrical communication and physical contact. Electricalcurrent associated with transferred arc operation of the torch 1020passes between the electrode body 1022 and the contact element 1002.

FIG. 11A depicts an exemplary contact element for use in a contact startplasma arc torch. The contact element 1100 includes a first surface1102, a second surface 1104, an extensive portion 1106 and a restrainingportion 1108. The first surface 1102 is configured for electricalcommunication with a power contact of a plasma arc torch (not shown).For example, electrical communication can be established by physicalcontact with a corresponding surface (not shown) of the power contact.The second surface 1104 is configured for electrical communication withan electrode body (not shown), a resilient conductive element, or both.For example, electrical communication can be established with theelectrode body by physical contact between the second surface 1104 and acorresponding surface of the electrode body. In some embodiments,physical contact between the power contact and the first surface 1102and physical contact between the electrode body and the second surfaceestablishes a path for current to flow between the power contact (e.g.,the power supply) and the electrode body.

The extensive portion 1106 of the contact element is adjacent therestraining portion 1108. In some embodiments, the extensive portion andthe restraining portion are formed integrally (e.g., from the samematerial). The extensive portion 1106 protrudes orthogonally from thesecond surface 1104. As depicted, the extensive portion 1106 defines acircular cross-section having a diameter, but other geometries arepossible. The width w of the restraining portion 1108 exceeds thediameter of the extensive portion 1106, and the thickness t of therestraining portion 1108 is less than the diameter.

FIG. 11B depicts the contact element of FIG. 11A rotated 90° about avertical axis. In some embodiments, the restraining portion 1108 and theextensive portion 1106 are advanced into a receptacle of an electrodebody (not shown) in a first orientation such as that of FIG. 11B. Anopening adjacent the receptacle is dimensioned to permit the restrainingportion 1108 and the extensive portion 1106 to enter the receptacle.However, rotating the contact element 1100 about a vertical axis (e.g.,as depicted in FIG. 1A), positions the contact element 1100 such thatthe restraining portion 1108 reacts against a portion of the receptacleto hinder disengagement of the contact element from the electrode body.The contact element 1100 can be secured to an electrode body in otherways, for example, by threading or by an interference fit.

FIG. 12A is a cross-sectional partial perspective view of an assembly1200 for a contact start plasma arc torch. The assembly 1200 includes anelectrode 1204, a hollow body 1208, a resilient element 1212, and apower contact 1216. The electrode 1204 includes an electrode body 1220including a distal end 1224 for housing an emissive element 1228. Theelectrode 1204 also includes an end 1232 positioned remotely from thedistal end 1224. The end 1232 is positioned relative to the distal end1224 (e.g., adjacent the electrode body 1220). The electrode body 1220includes a set of spiral-shaped grooves 1236 for directing gas flow orfacilitating cooling of the assembly 1200. The electrode 1204 can movealong axis A when the assembly 1200 is installed within a torch (notshown), for example, to slideably engage an interior surface 1240 of thehollow body 1208. The hollow body 1208 includes a front portion 1244 anda rear portion 1248. In one embodiment, the front portion 1244 includesone or more holes 1252 from an exterior surface 1256 to the interiorsurface 1240. The holes 1252 can impart a swirling motion relative tothe axis A to a gas flowing through the assembly 1200. A hollow body1208 having such holes 1252 for generating a swirl gas flow is commonlyreferred to as a swirl ring. It should be recognized that a swirl ringis simply a variation of a hollow body 1208 and the system disclosedherein is capable of function in the hollow body 1208 or swirl ringconfiguration. It should also be recognized that the hollow body may bean integrally formed portion of a torch.

The end 1232 of the electrode 1204 includes a portion 1260 that extendsaxially along axis A. The portion 1260 includes a first length 1264 (ordistance) along a first direction (e.g., radially away from the axis A)and a second length 1268 (or distance) along a second direction (e.g.,radially away from the axis A and perpendicular to the first direction).The hollow body 1208 includes a shoulder 1272 disposed relative to theinterior surface 1240 (e.g., defined on the interior surface 1240). Theshoulder 1272 can also be referred to as a contour, step, or flange andcan have various geometries relative to the interior surface 1240 (e.g.,semicircular, triangular, rectangular, or non-regular polygonalgeometries). The shoulder 1272 defines a first portion 1276 and a secondportion 1280. The first portion 1276 and the second portion 1280cooperate to form a contoured opening through which the portion 1260 ofthe electrode 1240 can move. More specifically, the second portion 1280is located at a distance from the axis A sufficient to facilitateslideable passage of the second length 1268 therethrough. The firstportion 1276 cooperates with the second portion 1280 to define anopening having a slot 1284 of sufficiently greater size than the firstlength 1264 to facilitate slideable passage of the first length 1264therethrough. The electrode 1204 is installed within the torch in thehollow body 1208 such that the portion 1260 can move axially along axisA and reciprocatingly through the opening defined by the first portion1276 and the second portion 1280.

The portion 1260 also includes a surface 1288 that includes a firstregion 1290 for electrical communication with the resilient element 1212and a second region 1292 for electrical communication with the powercontact 1216, e.g., via physical contact with a corresponding surface1294 of the power contact 1216. The resilient element 1212 resilientlyurges the electrode 1204 toward the distal end 1224. The electrode 1204is hindered from being ejected from the torch by a nozzle (not shown)that is in physical contact with the distal end 1224 when the nozzle isinstalled. The nozzle is secured to the torch so that the portion 1260(e.g., via the first region 1290) is in physical contact with theresilient element 1212. For example, installing the nozzle urges theportion 1260 through the slot 1284 and positions the first region 1290in physical contact with the resilient element 1212. When the nozzle isinstalled, the resilient element is compressed.

The resilient element 1212 is positioned between the shoulder 1272 and aflange 1296 of the power contact 1216. The resilient element 1212 isretained or captured between the hollow body 1208 (e.g., via theshoulder 1272) and the power contact 1216 (e.g., via the flange 1296).The shoulder 1272 thus retains the resilient element 1212 andfacilitates access by the electrode 1204 to the resilient element 1212and the power contact 1216.

The power contact 1216 is in electrical communication with a powersupply (not shown). During pilot arc initiation, the power supplyprovides a pilot arc current to the power contact 1216, and the currentflows from the flange 1296 through the resilient element 1212 to thefirst region 1290 of the electrode 1204. A plasma gas (not shown) flowsabout the electrode during pilot arc initiation, and the plasma gasincreases fluid pressure on the electrode 1204. The pressure moves theelectrode 1204 axially toward the power contact 1216 and into physicalcontact. Physical separation of the electrode 1204 and the nozzlegenerates a pilot arc in a plasma chamber (not shown) formed between thenozzle and the electrode 1204. Pressure moves the electrode 1204 intophysical contact and electrical communication with the power contact1216 for transferred arc operation. When the electrode 1204 is incontact with the power contact, the portion 1260 is disposed within theslot 1284.

During transferred arc operation, transferred arc current flows from thepower supply through the power contact 1216 to the electrode 1204 viathe physical contact between the second region 1292 of the surface 1288of the portion 1260 and the corresponding surface 1294 of the powercontact 1216. Gas pressure is increased during transferred arc operationto form a plasma jet for processing a workpiece (not shown).

Although the assembly 1200 is illustrated for the first region 1290 tophysically contact the resilient element 1212 directly, otherconfigurations are possible. For example, the resilient element 1212 caninclude a separate contact surface (not shown), such as an annular,washer-like plate, secured to the resilient element 1212 for physicalcontact and electrical communication with the electrode 1204. Similarly,the corresponding surface 1294 of the power contact 1216 can be platedor coated with a material such that the electrode 1204 is in contactwith the plate or coating rather than the power contact 1216 itself.Such configurations are within the scope of the invention.

In some embodiments, the front portion 1244 and the rear portion 1248 ofthe hollow body 1208 are integrally formed (e.g., manufactured from thesame piece of material). In some embodiments, the front portion 1244 andthe rear portion 1248 are formed of different materials, for example,the front portion 1244 can be made from an insulative material, and therear portion 1248 can be made from a conductive material.

In some embodiments, the slot 1284 has a dimension or size that issubstantially greater than the first length 1264 to facilitate someangular displacement of the electrode 1204 about the axis A within thehollow body 1208 (e.g., while the portion 1260 is disposed within theslot 1284). The slot 1284 can also resist angular displacement of theelectrode 1204 about the axis A, for example, by reacting against theportion 1260 to hinder angular displacement. In some embodiments, thefirst region 1290 and the second region 1292 of the surface 1288 are notco-planar or do not form regions of the same surface. For example, thefirst region 1290 can be positioned axially remote from the secondregion 1292, such that the portion 1260 of the electrode 1204 includesan axial step, flange, or shoulder (not shown).

FIG. 12B is an exploded perspective view of the assembly 1200 of FIG.12A with a portion of the hollow body 1208 cut away. The view of FIG.12B illustrates the electrode 1204, the hollow body 1208, the resilientelement 1212, and the power contact 1216 in an unassembled configurationbefore installation in a plasma arc torch (not shown). During assembly,the electrode 1204 slideably engages the hollow body 1208, such that nothreads are needed to attach the electrode 1204 to the hollow body 1208.A surface 1297 of the resilient element 1212 is illustrated. The surface1297 is in contact with the shoulder 1272 of the hollow body 1208 whenthe resilient element 1212 is positioned within the torch. The firstregion 1290 is moved through the slot 1284 and into physical contact andelectrical communication with at least a portion of the surface 1297 ofthe resilient element 1212.

FIG. 12C is an elevational view of a portion of the assembly 1200 ofFIG. 12A. FIG. 12C depicts the hollow body 1208, the power contact 1216,and the surface 1297 of the resilient element 1212. The electrode 1204is not shown, but reference is made to various features of the electrode1204 as depicted in FIG. 12A. The hollow body 1208 includes the shoulder1272. The shoulder 1272 defines a first portion 1276 and a secondportion 1280 that cooperate to form a contoured opening through whichthe portion 1260 of the electrode 1204 can move. As depicted, the firstportion 1276 and second portion 1280 cooperate to form the slots 1284Aand 1284B in the opening through which the portion 1260 of the electrode1204 can move (e.g., by reciprocatingly sliding) when the electrode 1204is installed in the torch. In such a configuration, the slots 1284A and1284B in the hollow body 1208 have a complimentary shape to the shape ofthe portion 1260 of the electrode. The shape of the slots 1284A and1284B are complimentary in that they are shaped to receive the portion1260 of the electrode. However, the shape of the slots 1284A and 1284Bneed not match the shape of the portion 1260 of the electrode. Instead,the shape of the slots 1284A and 1284B need only be capable of allowingclearance of the portion 1260 of the electrode.

In some embodiments, the first portion 1276 and the second portion 1280cooperate to form a contoured opening having one slot 1284A or 1284B,but not both. Each of the slots 1284A and 1284B are defined by twoportions 1285 that are parallel to each other. The portions 1285 canalso define other geometries or orientations, for example, the portions1285 can be radially directed relative to the axis A (e.g., to form atriangular slot 1284). The portions 1285 can also be circular,semicircular, or otherwise curved. In general, the portions 1285 candefine any geometry that permits the portion 1260 of the electrode topass through the shoulder 1272 (e.g., through the opening defined by thefirst portion 1276 and the second portion 1280).

The distance d₁ from the axis A to the second portion 1280 is greaterthan the distance d₂ from the axis A to the first portion 1276. Thedistance d₃ from the axis A to the resilient element 1212 is greaterthan the distance d₂ and less than the distance d₁. In some embodiments,the distance d₃ can be less than the distance d₂ (e.g., when an annularplate (not shown) is secured to the resilient element 1212). Thedistance d₄ from the axis A to the power contact 1216 is less than thedistance d₃ to facilitate passage of the second region 1292 through theresilient element 1212 and into physical contact and electricalcommunication with the corresponding surface 1294 of the power contact1216.

In some embodiments, the electrode 1204 does not move past the shoulder,for example, when the portion 1260 and the slots 1284A and 1284B are notaligned. In such configurations, the portion 1260 contacts the shoulder1272, which resists passage of the portion 1260 therethrough. In someembodiments, the electrode 1204 can be securely positioned within thetorch. For example, the portion 1260 can be passed entirely through theshoulder 1272 into contact with the resilient element 1212 (e.g., viathe first region 1290). The portion 1260 compresses the resilientelement 1212. The resilient element 1212 urges the electrode 1204 towardthe distal end 1224. Upon angular displacement of the portion 1260 aboutthe axis A, a proximal surface (not shown) of the shoulder 1272 resistsdistal movement of the electrode 1204. The interaction between theportion 1260 and the proximal surface of the shoulder 1272 prevents theresilient element 1212 from ejecting the electrode 1204 from the hollowbody 1208 and/or the torch.

In some embodiments, the portion 1260 has a circular configurationcentered about the axis A. In such embodiments, the portion 1260includes a first region 1290 (e.g., an annular outer perimeter of thecircular configuration) for physical contact and electricalcommunication with the resilient element 1212 and a second region 1292(e.g., a region disposed within the annular outer perimeter) forelectrical communication and physical contact with the power contact1216. As discussed above, the first region 1290 and the second region1292 can be co-planar (e.g., portions of the same surface) ornon-co-planar (e.g., portions of different surfaces). In an alternativeembodiment, the first region 1290 can be a separate radial extensiveportion (not shown) positioned along the length of the longitudinal axisA of the electrode 1204, such as a pin extending radially through theelectrode 1204. The radial extensive portion functions in the samemanner as the first region 1290, by providing a mechanism forelectrically coupling the electrode 1204 to a resilient element 1212 forconducting a pilot arc. In one embodiment, the radial extensive portionis an elongated shoulder or a pin that can pass through shoulder 1272,while still allowing the resilient element 1212 to be maintained withinthe hollow body 1208. In such an embodiment, the shoulder 1272 ispositioned further down the axial length of the hollow body 1208 towardsthe distal end of the electrode.

FIG. 13A is a perspective view of an electrode 1300 for a contact startplasma arc torch. The electrode 1300 is similar to the electrode 1204depicted in FIG. 12A. The electrode includes a distal end 1304 and asecond end 1308. The second end 1308 includes an extensive portion 1312that extends axially along the axis A. The extensive portion 1312defines three portions 1316A, 1316B, and 1316C (also called “fins”), allof which extend away from the axis A. Each of the three portions 1316A,1316B, and 1316C define a first length l₁ and a second length l₂ that isgreater than the first length l₁. In some embodiments, the values forthe first length l₁ and second length l₂ of each of the three portions1316A, 1316B, and 1316C are the same. The values for the first length l₁and the second length l₂ can also be different for each of the threeportions 1316A, 1316B, and 1316C. The lengths l₁ and l₂ are depicted asdirected perpendicularly to each other. In some embodiments, the lengthsl₁ and l₂ can be directed in other configurations, for example, radiallyaway from the axis A towards points 1320A and 1320B respectively. Otherdirections for the lengths l₁ and l₂ are also possible.

As depicted, each of the three portions 1316A, 1316B, and 1316C aredisposed about the axis A in an equiangular configuration (e.g., anangle θ between each of the portions 1316A, 1316B, and 1316C is about120°). However, the three portions 1316A, 1316B, and 1316C can bedisposed in other angular configurations about the axis A that are notequiangular.

Each of the three portions 1316A, 1316B, and 1316C include a respectivefirst region 1324A, 1324B, and 1324C for electrical communication and/orphysical contact with a corresponding surface (not shown) of a resilientelement (not shown). Each of the three portions 1316A, 1316B, and 1316Cinclude a respective second region 1328A, 1328B, and 1328C forelectrical communication and/or physical contact with a correspondingsurface (not shown) of a power contact (not shown).

As depicted, the first region 1324A, 1324B, and 1324C of each portion1316A, 1316B, and 1316C is depicted as coplanar with the respectivesecond portion 1328A, 1328B, and 1328C. In some embodiments, the firstregion 1324A, 1324B, and 1324C is not coplanar with the respectivesecond region 1328A, 1328B, and 1328C. In some embodiments, the secondregions 1328A, 1328B, and 1328C are not coplanar with each other secondregion. In some embodiments, a subset of the three portions, e.g., 1316Aand 1316B, are in electrical communication with the resilient element,and the other portions, e.g., 1316C, is not in electrical communicationwith the resilient element. The portions, e.g., 1316C, not in electricalcommunication with the resilient element can provide aligning featuresor increased surface area to improve cooling the electrode. The portion1316C can still be moved into physical contact and electricalcommunication with the power contact during transferred arc operation.In some embodiments, the first region 1324A, 1324B, and 1324C or thesecond region 1328A, 1328B, and 1328C, or both, can coincide with theextensive portion 1312. For example, pilot current and/or transferredarc current can flow between a power supply and the electrode 1300 viaelectrical communication with the extensive portion 1312 (e.g., via asliding electrical contact discussed above).

FIG. 13B is an elevational view of an assembly 1340 for use with theelectrode 1300 of FIG. 13A. The assembly 1340 includes a hollow body1344, a resilient element 1348, and a power contact 1352. The assemblyis similar to the assembly 1200 depicted in FIG. 12C. The assembly 1340is configured for use with the electrode 1300 of FIG. 13A. Morespecifically, hollow body 1344 includes a shoulder 1356 that has a firstportion 1360 and a second portion 1364 that cooperate to form acontoured opening having three slots 1368A, 1368B, and 1368C. Theopening and the three slots 1368A, 1368B, and 1368C facilitate movementof the corresponding portions 1316A, 1316B, and 1316C through theopening and into physical contact and electrical communication with theresilient element 1348. As discussed above, the size of slots 1368A,1368B, and 1368C is depicted as approximately the same size as theportions 1316A, 1316B, and 1316C; however, the slots 1368A, 1368B, and1368C can be larger (e.g., circumferentially larger) than thecorresponding portions 1316A, 1316B, and 1316C.

FIGS. 14A-14B, 15A-15B, and 16 depict alternative embodiments ofelectrodes and assemblies that operate similarly to those describedabove.

FIG. 14A is a perspective view of an electrode 1400 for a contact startplasma arc torch. The electrode 1400 includes four portions 1404A,1404B, 1404C, and 1404D.

FIG. 14B is an elevational view of an assembly 1420 for use with theelectrode 1400 of FIG. 14A. The assembly 1420 includes a hollow body1424 including a shoulder 1428 with a first portion 1432 and a secondportion 1436 defining an contoured opening with four slots 1440A, 1440B,1440C, and 1440D to facilitate passage of the four correspondingportions 1404A, 1404B, 1404C, and 1404D through the contoured openingand into physical contact and/or electrical communication with theresilient element 1444 and the power contact 1448.

FIG. 15A is a perspective view of an electrode 1500 for a contact startplasma arc torch. The electrode 1500 includes five portions 1504A,1504B, 1504C, 1504D, and 1504E.

FIG. 15B is an elevational view of an assembly 1520 for use with theelectrode 1500 of FIG. 15A. The assembly 1520 includes a hollow body1524 including a shoulder 1528 defining a contoured opening tofacilitate passage of the five corresponding portions 1504A, 1504B,1504C, 1504D, and 1504E through the contoured opening and into physicalcontact and/or electrical communication with a resilient element 1532and power contact 1536. The electrode 1500 can be used in a mannersimilar to that described above for the electrode 1204 of FIG. 12A,electrode 1300 of FIG. 13A, and the electrode 1400 of FIG. 14A.

A value for the operational current of the plasma arc torch can berelated or associated with the number of portions (e.g., the threeportions 1316A-1316C of FIG. 13A, the four portions 1404A-1404D of FIG.14A, or the five portions 1504A-1504E of FIG. 15A) that a particularelectrode includes. For example, an electrode with the three portions1316A-1316C can be used in a torch operating at about 60 Amps duringtransferred arc operation. An electrode with four portions 1404A-1404Dcan be used in a torch operating at about 80 Amps during transferred arcoperation. An electrode with five portions 1504A-1504E can be used in atorch operating at about 100 Amps during transferred arc operation.Electrodes employing the designs depicted in FIGS. 13A, 14A, and 15A canbe used in torches configured with a contoured opening as depicted inFIGS. 13B, 14B, and 15B, respectively. In some embodiments, an electrodecan include more than five portions.

By correlating the number of fins to the torch operating current, theusage of the correct electrode for a given operating current of thetorch can be assured. By way of example, in the operation of a 60-Amptorch, the use of a hollow body 1344 with three slots 1368A, 1368B, and1368C will receive a 60-Amp electrode with a corresponding number ofportions (or “fins”), e.g., the three portions 1316A-1316C. On the otherhand, if a user attempts to use a 100-Amp electrode, e.g., an electrode1500 with five portions 1504A-1504E, in an 60-Amp torch configured withthe three slots 1368A, 1368B, and 1368C, the electrode 1500 and thehollow body 1344 would not mate. The five portions 1504A-1504E arehindered from passing through the three slots 1368A-1368C. By employingsuch a system, the particular torch can be optimized for a particularelectrode. In some embodiments, a user is thus prevented from using anelectrode with five fins (e.g., the electrode 1500) with a torch that isnot optimized for that electrode (e.g., a torch having three slots1368A-1368C). Moreover, an electrode (e.g., the electrode 1300) havingfewer fins (e.g., three portions 1316A-1316-C) is hindered from use witha torch employing more slots (e.g., the five slots of the hollow body1524), which increases the operational of life of the electrode byoptimizing the amount of current flowing through the electrode.

FIG. 16 is a perspective view of an electrode 1600 for a contact startplasma arc torch. The electrode 1600 includes a distal end 1604 and asecond end 1608. The second end 1608 includes an extensive portion 1612that defines a surface 1616 having diameter d₁. Two regions 1620A and1620B extend from the surface 1616 along an axis A. The regions 1620Aand 1620B each define a respective end surface 1624A and 1624B. The endsurfaces 1624A and 1624B can be used for physical contact and electricalcommunication with a corresponding surface of a resilient element (e.g.,the surface 1297 of the resilient element 1212 of FIG. 12C). Current forpilot arc initiation flows between the resilient element (not shown) andthe electrode 1600 via the surfaces 1624A and 1624B and the regions1620A and 1620B. As the electrode 1600 is moved in a proximal direction(e.g., away from the distal end 1604) during pilot arc initiation, theregions 1620A and 1620B compress the resilient element. The surface 1616is moved into physical contact and electrical communication with acorresponding surface (not shown) of a power contact (not shown), suchas the surface 1294 of the power contact 1216 of FIG. 12A fortransferred arc operation.

The regions 1620A and 1620B also define respective extensive surfaces1628A and 1628B. The regions 1620A and 1620B can pass through the slots1284A and 1284B of FIG. 12C (e.g., the slots 1284A and 1284B defined bythe first portion 1276 and the second portion 1280 of the shoulder1272). The extensive portions 1628A and 1628B can react against theslots 1284A and 1284B to hinder or resist angular displacement of theelectrode 1600 about the axis A within the torch. As depicted, theregions 1620A and 1620B substantially parallel to the axis A. Otherconfigurations or alignments of the regions 1620A and 1620B can be used.Each of the regions 1620A and 1620B defines a diameter d₂ that issmaller than the diameter d₁.

In some embodiments, a second extensive portion (not shown) extends fromthe surface 1616 and defines a second surface (not shown). The secondsurface can be parallel to the surface 1616. The second extensiveportion can extend distally (e.g., towards the distal end 1604) todefine a cavity (not shown) within the second end 1608 relative to thesurface 1616. The second extensive portion can extend proximally (e.g.,away from the distal end 1604) to define a cylindrical or pedestal-likeportion (not shown). In such embodiments, the second surface can bemoved into physical contact and electrical communication with acorresponding surface of the power contact for transferred arcoperation.

The regions 1620A and 1620B are disposed diametrally opposite each otherand equidistant from the axis A. In some embodiments, the electrode 1600includes more than two regions 1620A and 1620B (e.g., three, four, orfive regions, for use with the assemblies 1340, 1420, and 1520 of FIGS.13B, 14B, and 15B, respectively). In some embodiments, the electrode1600 includes only one region 1620A or 1620B. In such embodiments, theregion 1620A or 1620B can be parallel or aligned with the axis A. Theshoulder (e.g., the shoulder 1272) can define an opening having asubstantially continuous circumference (e.g., without the slot 1284) insuch an embodiment. The diameter of the opening can be smaller than anouter diameter of the resilient element and larger than an innerdiameter of the resilient element to hinder removal of the resilientelement from the torch. The region 1620A or 1620B defines a diametersmaller than the diameter of the opening but larger than the innerdiameter of the resilient element to facilitate contact between theregion 1620A or 1620B and the resilient element.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. For example, while some surfaces havebeen depicted as planar, surfaces having other, non-planar geometries,such as, spherical, hemispherical, conical, and/or cylindricalgeometries may be used without departing from the spirit and the scopeof the invention.

What is claimed is:
 1. An electrode for a contact start plasma arc torchin electrical communication with a power supply, the electrode beingmovable relative to a nozzle within a plasma chamber of the torch, theelectrode comprising: an elongated electrode body formed of anelectrically conductive material, the electrode body defining alongitudinal axis; and a resilient element contacting a proximal end ofthe electrode body and imparting a separation force to the electrodebody, wherein the electrode body is adapted to overcome the separationforce and engage a contact element of the torch when the torch isoperated in a transferred arc mode.
 2. The electrode of claim 1, whereinthe electrode body further comprises a reaction surface disposed in aspaced relationship relative to the proximal end of the electrode body,wherein the reaction surface is configured for electrical communicationwith the resilient element.
 3. The electrode of claim 2, wherein thereaction surface comprises a radially extending flange formed integrallywith the electrode body.
 4. The electrode of claim 1, wherein theresilient element is secured relative to the proximal end of theelectrode body.
 5. The electrode of claim 1, wherein the resilientelement is secured by a diametral interference fit.
 6. The electrode ofclaim 1, wherein the resilient element is formed integrally with theelectrode body.
 7. The electrode of claim 1, further comprising a hollowbody for maintaining the resilient element and slideably receiving theelectrode body.
 8. The electrode of claim 7, wherein the hollow body isa swirl ring.
 9. The electrode of claim 1, wherein the contact elementincludes a first surface and a second surface, the first surfacefacilitating electrical communication with the power supply and thesecond surface is characterized by physical contact with the electrodebody when the torch is operated in the transferred arc mode.
 10. Theelectrode of claim 9, wherein the second surface of the contact elementis characterized by absence of physical contact with the electrode bodyduring initiation of a pilot arc.
 11. The electrode of claim 9, whereinthe contact element further comprises a connective member extending fromthe second surface to slideably engage the electrode body.
 12. Theelectrode of claim 11, wherein the connective member is formedintegrally with the second surface.
 13. The electrode of claim 11,wherein the contact element further comprises an aligning portiondefining an axis, the aligning portion disposed in a spaced relationshipwith the proximal end of the electrode body and configured to restrainradial movement of the electrode body.
 14. The electrode of claim 11,wherein a portion of the contact element facilitates passage of a pilotarc current between the contact element and the electrode body when thecontact element slideably engages the electrode body.
 15. The electrodeof claim 1, wherein the resilient element passes at least substantiallyall of a pilot arc current between the power supply and the electrodebody.
 16. The electrode of claim 1, wherein the resilient element is notelectrically conductive.
 17. The electrode of claim 16, furthercomprising a conductive element for passing at least substantially allof a pilot arc current between the power supply and the electrode body.18. An electrode for a contact start plasma arc torch in electricalcommunication with a power supply, the electrode being movable relativeto a nozzle within a plasma chamber of the torch, the electrodecomprising: an elongated electrode body formed of an electricallyconductive material and defining a longitudinal axis, the electrode bodycomprising: a first surface characterized by i) physical contact with acontact element when the torch is operated in a transferred arc mode andii) absence of physical contact with the contact element duringinitiation of a pilot arc; and a second surface positioned remotely fromthe first surface, the second surface contacting a resilient elementconfigured to impart a separation force between the electrode body andthe contact element.
 19. The electrode of claim 18, wherein the contactelement comprises an annular configuration.
 20. The electrode of claim18, further comprising a receptacle disposed within the proximal end ofthe electrode body for receiving at least a portion of the contactelement such that a first portion of the contact element is physicallyremote from the electrode body during initiation of a pilot arc, thefirst portion for passing at least substantially all of a transferredarc current between the power supply and the electrode body at the firstsurface when the torch is operated in the transferred arc mode.
 21. Theelectrode of claim 20, wherein the receptacle further comprises: acylindrical portion; and a restraint surface disposed at a proximal endof the receptacle for reacting against a portion of the contact elementto hinder disengagement of the contact element from the receptacle. 22.The electrode of claim 21, wherein the restraint surface comprises anannular configuration.
 23. The electrode of claim 21, wherein thecylindrical portion is defined by a first diameter, the restraintsurface comprises a second diameter, and a distal region of a connectivemember of the contact element defines a third diameter, such that thethird diameter is greater than the second diameter and less than thefirst diameter.
 24. The electrode of claim 23, wherein the distal regionis a distal end of the connective member.
 25. The electrode of claim 20,wherein the resilient element is retained by the electrode body.
 26. Theelectrode of claim 25, wherein the resilient element is retained by adiametral interference fit.
 27. The electrode of claim 25, wherein theresilient element is disposed within the receptacle.
 28. The electrodeof claim 18, wherein the second surface comprises a radially extendingflange formed integrally with the electrode body.
 29. A contact startplasma arc torch comprising: a power supply for providing current to thetorch; a plasma chamber defined by a nozzle and an electricallyconductive electrode body slideably mounted within the torch anddefining a longitudinal axis; a power contact disposed in a stationaryposition relative to the plasma chamber, the power contact in electricalcommunication with the power supply; and a resilient element contactinga proximal end of the electrode body and imparting a separation force tothe electrode body, wherein the electrode body is adapted to overcomethe separation force and engage the power contact when the torch isoperated in a transferred arc mode.
 30. The plasma arc torch of claim29, further comprising a swirl ring that imparts radial motion to a gasflowing through the torch.
 31. The plasma arc torch of claim 29, furthercomprising a shield defining an exit port positioned adjacent an exitorifice of the nozzle, the shield mounted on a retaining cap supportedon a torch body of the plasma arc torch.
 32. The plasma arc torch ofclaim 29, wherein the power contact passes at least substantially all ofa transferred arc current between the power supply and the electrodebody when the torch is operated in the transferred arc mode.
 33. Theplasma arc torch of claim 29, wherein the resilient element passes atleast substantially all of a pilot arc current between the power supplyand the electrode body when the torch is operated in a pilot arc mode.34. The plasma arc torch of claim 29, further comprising a conductiveelement for passing at least substantially all of a pilot arc currentbetween the power supply and the electrode body when the torch isoperated in a pilot arc mode, wherein the resilient element is notelectrically conductive.